Which statement is TRUE of a gasoline spill ________．A.It is visible for a shorter time than a fuel oil spillB.It is not covered by the pollution lawsC.It does little harm to marine lifeD.It will sink more rapidly than crude oil
Which statement is TRUE of a gasoline spill ________．
A.It is visible for a shorter time than a fuel oil spill
B.It is not covered by the pollution laws
C.It does little harm to marine life
D.It will sink more rapidly than crude oil
相关考题：
_______can cause oil flow from water outlet of the oil purifier.A.Oil inlet valve opening too quicklyB.Oil temperature little higher than normalC.Diameter of gravity disc too smallD.Viscosity of oil little lower than normal
Which substance is NOT considered to be Oil under the pollution prevention regulations?A.Petroleum and fuel oilB.SludgeC.Oil mixed with dredge spoilD.Oil refuse and oil mixed with wastes
Certificate of insurance or other financial security in respect of civil liability for oil pollution damage shall be carried on board by ______．A.ships carrying more than 2000 tons of oil in bulk as cargoB.oil tankersC.bulk chemicals carriersD.liquefied gas carriers
共用题干第三篇Oil and EconomyCould the bad old days of economic decline be about to return?Since OPEC agreed to supplycuts in March,the price of crude oil has jumped to almost $26 a barrel,up from less than$10 last December. This near-tripling of oil prices calls up scary memories of the 1973 oil shock,when prices quadrupled,and 1979一1980,when they also almost tripled.Both previous shocks resulted in double一digit inflation and global economic decline.So where are the headlines warning of gloom and doom this time?The oil price was given another push up this week when Iraq suspended oil exports.Strengthening economic growth,at the same time as winter grips the northern hemisphere,could push the price higher still in the short term.Yet there are good reasons to expect the economic consequences now to be less severe than in the 1970s.In most countries the cost of crude oil now accounts for a smaller share of the price of petrol than it did in the 1970s.In Europe,taxes account for up to four-fifths of the retail price,so even quite big changes in the price of crude oil have a more muted effect on pump prices than in the past.Rich economies are also less dependent on oil than they were,and so less sensitive to swings in the oil price.Energy conservation,a shift to other fuels and a decline in the importance of heavy, energy-intensive industries have reduced oil consumption.Software,consultancy and mobile telephones use far less oil than steel or car production.For each dollar of GDP(in constant prices)rich economies now use nearly 50%less oil than in 1973.The OECD estimates in its latest Economic Outlook that,if oil prices averaged $22 a barrel for a full year,compared with $13 in 1998,this would increase the oil import bill in rich economies by only 0.25-0.S%of GDP. That is less than one-quarter of the income loss in 1974 or 1980.On the other hand,oil-importing emerging economies一to which heavy industry has shifted一have become more energy一intensive,and so could be more seriously squeezed.One more reason not to lose sleep over the rise in oil prices is that,unlike the rises in the 1970s,it has not occurred against the background of general commodity-price inflation and global excess demand.A sizable portion of the world is only just emerging from economic decline.The Economist's commodity price index is broadly unchanging from a year ago. In 1973 commodity prices jumped by 70%,and in 1979 by almost 30%.The estimates in Economic Outlook show that in rich countries______.A:heavy industry becomes more energy-intensiveB:income loss mainly results from fluctuating crude oil pricesC:manufacturing industry has been seriously squeezedD:oil price changes have no significant impact on GDP
共用题干第三篇Oil and EconomyCould the bad old days of economic decline be about to return?Since OPEC agreed to supplycuts in March,the price of crude oil has jumped to almost $26 a barrel,up from less than$10 last December. This near-tripling of oil prices calls up scary memories of the 1973 oil shock,when prices quadrupled,and 1979一1980,when they also almost tripled.Both previous shocks resulted in double一digit inflation and global economic decline.So where are the headlines warning of gloom and doom this time?The oil price was given another push up this week when Iraq suspended oil exports.Strengthening economic growth,at the same time as winter grips the northern hemisphere,could push the price higher still in the short term.Yet there are good reasons to expect the economic consequences now to be less severe than in the 1970s.In most countries the cost of crude oil now accounts for a smaller share of the price of petrol than it did in the 1970s.In Europe,taxes account for up to four-fifths of the retail price,so even quite big changes in the price of crude oil have a more muted effect on pump prices than in the past.Rich economies are also less dependent on oil than they were,and so less sensitive to swings in the oil price.Energy conservation,a shift to other fuels and a decline in the importance of heavy, energy-intensive industries have reduced oil consumption.Software,consultancy and mobile telephones use far less oil than steel or car production.For each dollar of GDP(in constant prices)rich economies now use nearly 50%less oil than in 1973.The OECD estimates in its latest Economic Outlook that,if oil prices averaged $22 a barrel for a full year,compared with $13 in 1998,this would increase the oil import bill in rich economies by only 0.25-0.S%of GDP. That is less than one-quarter of the income loss in 1974 or 1980.On the other hand,oil-importing emerging economies一to which heavy industry has shifted一have become more energy一intensive,and so could be more seriously squeezed.One more reason not to lose sleep over the rise in oil prices is that,unlike the rises in the 1970s,it has not occurred against the background of general commodity-price inflation and global excess demand.A sizable portion of the world is only just emerging from economic decline.The Economist's commodity price index is broadly unchanging from a year ago. In 1973 commodity prices jumped by 70%,and in 1979 by almost 30%.We can draw a conclusion from the text that______.A:oil-price shocks are less shocking nowB:inflation seems irrelevant to oil-price shocksC:energy conservation can keep down the oil pricesD:the price rise of crude oil leads to the shrinking of heavy industry
共用题干第三篇Oil and EconomyCould the bad old days of economic decline be about to return?Since OPEC agreed to supplycuts in March,the price of crude oil has jumped to almost $26 a barrel,up from less than$10 last December. This near-tripling of oil prices calls up scary memories of the 1973 oil shock,when prices quadrupled,and 1979一1980,when they also almost tripled.Both previous shocks resulted in double一digit inflation and global economic decline.So where are the headlines warning of gloom and doom this time?The oil price was given another push up this week when Iraq suspended oil exports.Strengthening economic growth,at the same time as winter grips the northern hemisphere,could push the price higher still in the short term.Yet there are good reasons to expect the economic consequences now to be less severe than in the 1970s.In most countries the cost of crude oil now accounts for a smaller share of the price of petrol than it did in the 1970s.In Europe,taxes account for up to four-fifths of the retail price,so even quite big changes in the price of crude oil have a more muted effect on pump prices than in the past.Rich economies are also less dependent on oil than they were,and so less sensitive to swings in the oil price.Energy conservation,a shift to other fuels and a decline in the importance of heavy, energy-intensive industries have reduced oil consumption.Software,consultancy and mobile telephones use far less oil than steel or car production.For each dollar of GDP(in constant prices)rich economies now use nearly 50%less oil than in 1973.The OECD estimates in its latest Economic Outlook that,if oil prices averaged $22 a barrel for a full year,compared with $13 in 1998,this would increase the oil import bill in rich economies by only 0.25-0.S%of GDP. That is less than one-quarter of the income loss in 1974 or 1980.On the other hand,oil-importing emerging economies一to which heavy industry has shifted一have become more energy一intensive,and so could be more seriously squeezed.One more reason not to lose sleep over the rise in oil prices is that,unlike the rises in the 1970s,it has not occurred against the background of general commodity-price inflation and global excess demand.A sizable portion of the world is only just emerging from economic decline.The Economist's commodity price index is broadly unchanging from a year ago. In 1973 commodity prices jumped by 70%,and in 1979 by almost 30%.The main reason for the latest rise of oil price is______.A:global inflationB:reduction in supplyC:fast growth in economyD:Iraq's suspension of exports
共用题干第三篇Oil and EconomyCould the bad old days of economic decline be about to return?Since OPEC agreed to supplycuts in March,the price of crude oil has jumped to almost $26 a barrel,up from less than$10 last December. This near-tripling of oil prices calls up scary memories of the 1973 oil shock,when prices quadrupled,and 1979一1980,when they also almost tripled.Both previous shocks resulted in double一digit inflation and global economic decline.So where are the headlines warning of gloom and doom this time?The oil price was given another push up this week when Iraq suspended oil exports.Strengthening economic growth,at the same time as winter grips the northern hemisphere,could push the price higher still in the short term.Yet there are good reasons to expect the economic consequences now to be less severe than in the 1970s.In most countries the cost of crude oil now accounts for a smaller share of the price of petrol than it did in the 1970s.In Europe,taxes account for up to four-fifths of the retail price,so even quite big changes in the price of crude oil have a more muted effect on pump prices than in the past.Rich economies are also less dependent on oil than they were,and so less sensitive to swings in the oil price.Energy conservation,a shift to other fuels and a decline in the importance of heavy, energy-intensive industries have reduced oil consumption.Software,consultancy and mobile telephones use far less oil than steel or car production.For each dollar of GDP(in constant prices)rich economies now use nearly 50%less oil than in 1973.The OECD estimates in its latest Economic Outlook that,if oil prices averaged $22 a barrel for a full year,compared with $13 in 1998,this would increase the oil import bill in rich economies by only 0.25-0.S%of GDP. That is less than one-quarter of the income loss in 1974 or 1980.On the other hand,oil-importing emerging economies一to which heavy industry has shifted一have become more energy一intensive,and so could be more seriously squeezed.One more reason not to lose sleep over the rise in oil prices is that,unlike the rises in the 1970s,it has not occurred against the background of general commodity-price inflation and global excess demand.A sizable portion of the world is only just emerging from economic decline.The Economist's commodity price index is broadly unchanging from a year ago. In 1973 commodity prices jumped by 70%,and in 1979 by almost 30%.It can be inferred from the text that the retail price of petrol will go up dramatically in Europe if______.A:price of crude risesB:commodity prices riseC:consumption risesD:oil taxes rise
共用题干第三篇Oil and EconomyCould the bad old days of economic decline be about to return?Since OPEC agreed to supplycuts in March,the price of crude oil has jumped to almost $26 a barrel,up from less than$10 last December. This near-tripling of oil prices calls up scary memories of the 1973 oil shock,when prices quadrupled,and 1979一1980,when they also almost tripled.Both previous shocks resulted in double-digit inflation and global economic decline.So where are the headlines warning of gloom and doom this time?The oil price was given another push up this week when Iraq suspended oil exports.Strengthening economic growth,at the same time as winter grips the northern hemisphere,could push the price higher still in the short term.Yet there are good reasons to expect the economic consequences now to be less severe than in the l970s.In most countries the cost of crude oil now accounts for a smaller share of the price of petrol than it did in the l970s.In Europe,taxes account for up to four-fifths of the retail price,so even quite big changes in the price of crude have a more muted effect on pump prices than in the past.Rich economies are also less dependent on oil than they were,and so less sensitive to swings in the oil price.Energy conservation,a shift to other fuels and a decline in the importance of heavy, energy-intensive industries have reduced oil consumption.Software,consultancy and mobile telephones use far less oil than steel or car production.For each dollar of GDP(inconstant prices)in rich economies now use nearly 50%less oil than in 1973.The OECD estimates in its latest Economic Outlook that,if oil prices averaged $22 a barrel for a full year,compared with$13 in 1998,this would increase the oil import bill in rich economies by only 0.25％～0.5%of GDP.That is less than one-quarter of the income loss in 1974 or 1980. On the other hand,oil-importing emerging economies一to which heavy industry has shifted一have become more energy-intensive,and so could be more seriously squeezed.One more reason not to lose sleep over the rise in oil prices is that,unlike the rises in the 1970s,it has not occurred against the background of general commodity-price inflation and global excess demand.A sizable portion of the world is only just emerging from economic decline.The Economist's commodity price index is broadly unchanging from a year ago.In 1973 commodity prices jumped by 70%,and in 1979 by almost 30%.It can be inferred from the text that the retail price of petrol will go up dramatically if_______.A:price of crude risesB:commodity prices riseC:consumption risesD:oil taxes rise
共用题干第三篇Oil and EconomyCould the bad old days of economic decline be about to return?Since OPEC agreed to supplycuts in March,the price of crude oil has jumped to almost $26 a barrel,up from less than$10 last December. This near-tripling of oil prices calls up scary memories of the 1973 oil shock,when prices quadrupled,and 1979一1980,when they also almost tripled.Both previous shocks resulted in double-digit inflation and global economic decline.So where are the headlines warning of gloom and doom this time?The oil price was given another push up this week when Iraq suspended oil exports.Strengthening economic growth,at the same time as winter grips the northern hemisphere,could push the price higher still in the short term.Yet there are good reasons to expect the economic consequences now to be less severe than in the l970s.In most countries the cost of crude oil now accounts for a smaller share of the price of petrol than it did in the l970s.In Europe,taxes account for up to four-fifths of the retail price,so even quite big changes in the price of crude have a more muted effect on pump prices than in the past.Rich economies are also less dependent on oil than they were,and so less sensitive to swings in the oil price.Energy conservation,a shift to other fuels and a decline in the importance of heavy, energy-intensive industries have reduced oil consumption.Software,consultancy and mobile telephones use far less oil than steel or car production.For each dollar of GDP(inconstant prices)in rich economies now use nearly 50%less oil than in 1973.The OECD estimates in its latest Economic Outlook that,if oil prices averaged $22 a barrel for a full year,compared with$13 in 1998,this would increase the oil import bill in rich economies by only 0.25％～0.5%of GDP.That is less than one-quarter of the income loss in 1974 or 1980. On the other hand,oil-importing emerging economies一to which heavy industry has shifted一have become more energy-intensive,and so could be more seriously squeezed.One more reason not to lose sleep over the rise in oil prices is that,unlike the rises in the 1970s,it has not occurred against the background of general commodity-price inflation and global excess demand.A sizable portion of the world is only just emerging from economic decline.The Economist's commodity price index is broadly unchanging from a year ago.In 1973 commodity prices jumped by 70%,and in 1979 by almost 30%.We can draw a conclusion from the text that_______.A:oil-price shocks are less shocking nowB:inflation seems irrelevant to oil-price shocksC:energy conservation can keep down the oil pricesD:the price rise of crude leads to the shrinking of heavy industry
共用题干第三篇Oil and EconomyCould the bad old days of economic decline be about to return?Since OPEC agreed to supplycuts in March,the price of crude oil has jumped to almost $26 a barrel,up from less than$10 last December. This near-tripling of oil prices calls up scary memories of the 1973 oil shock,when prices quadrupled,and 1979一1980,when they also almost tripled.Both previous shocks resulted in double-digit inflation and global economic decline.So where are the headlines warning of gloom and doom this time?The oil price was given another push up this week when Iraq suspended oil exports.Strengthening economic growth,at the same time as winter grips the northern hemisphere,could push the price higher still in the short term.Yet there are good reasons to expect the economic consequences now to be less severe than in the l970s.In most countries the cost of crude oil now accounts for a smaller share of the price of petrol than it did in the l970s.In Europe,taxes account for up to four-fifths of the retail price,so even quite big changes in the price of crude have a more muted effect on pump prices than in the past.Rich economies are also less dependent on oil than they were,and so less sensitive to swings in the oil price.Energy conservation,a shift to other fuels and a decline in the importance of heavy, energy-intensive industries have reduced oil consumption.Software,consultancy and mobile telephones use far less oil than steel or car production.For each dollar of GDP(inconstant prices)in rich economies now use nearly 50%less oil than in 1973.The OECD estimates in its latest Economic Outlook that,if oil prices averaged $22 a barrel for a full year,compared with$13 in 1998,this would increase the oil import bill in rich economies by only 0.25％～0.5%of GDP.That is less than one-quarter of the income loss in 1974 or 1980. On the other hand,oil-importing emerging economies一to which heavy industry has shifted一have become more energy-intensive,and so could be more seriously squeezed.One more reason not to lose sleep over the rise in oil prices is that,unlike the rises in the 1970s,it has not occurred against the background of general commodity-price inflation and global excess demand.A sizable portion of the world is only just emerging from economic decline.The Economist's commodity price index is broadly unchanging from a year ago.In 1973 commodity prices jumped by 70%,and in 1979 by almost 30%.The estimates in Economic Outlook show that in rich countries_______.A:heavy industry becomes more energy-intensiveB:income loss mainly results from fluctuating crude oil pricesC:manufacturing industry has been seriously squeezedD:oil price changes have no significant impact on GDP
共用题干第三篇Oil and EconomyCould the bad old days of economic decline be about to return?Since OPEC agreed to supplycuts in March,the price of crude oil has jumped to almost $26 a barrel,up from less than$10 last December. This near-tripling of oil prices calls up scary memories of the 1973 oil shock,when prices quadrupled,and 1979一1980,when they also almost tripled.Both previous shocks resulted in double-digit inflation and global economic decline.So where are the headlines warning of gloom and doom this time?The oil price was given another push up this week when Iraq suspended oil exports.Strengthening economic growth,at the same time as winter grips the northern hemisphere,could push the price higher still in the short term.Yet there are good reasons to expect the economic consequences now to be less severe than in the l970s.In most countries the cost of crude oil now accounts for a smaller share of the price of petrol than it did in the l970s.In Europe,taxes account for up to four-fifths of the retail price,so even quite big changes in the price of crude have a more muted effect on pump prices than in the past.Rich economies are also less dependent on oil than they were,and so less sensitive to swings in the oil price.Energy conservation,a shift to other fuels and a decline in the importance of heavy, energy-intensive industries have reduced oil consumption.Software,consultancy and mobile telephones use far less oil than steel or car production.For each dollar of GDP(inconstant prices)in rich economies now use nearly 50%less oil than in 1973.The OECD estimates in its latest Economic Outlook that,if oil prices averaged $22 a barrel for a full year,compared with$13 in 1998,this would increase the oil import bill in rich economies by only 0.25％～0.5%of GDP.That is less than one-quarter of the income loss in 1974 or 1980. On the other hand,oil-importing emerging economies一to which heavy industry has shifted一have become more energy-intensive,and so could be more seriously squeezed.One more reason not to lose sleep over the rise in oil prices is that,unlike the rises in the 1970s,it has not occurred against the background of general commodity-price inflation and global excess demand.A sizable portion of the world is only just emerging from economic decline.The Economist's commodity price index is broadly unchanging from a year ago.In 1973 commodity prices jumped by 70%,and in 1979 by almost 30%.From the text we can see that the writer seems_______.A:optimistic B:sensitiveC:gloomy D:scared
共用题干第三篇Oil and EconomyCould the bad old days of economic decline be about to return?Since OPEC agreed to supplycuts in March,the price of crude oil has jumped to almost $26 a barrel,up from less than$10 last December. This near-tripling of oil prices calls up scary memories of the 1973 oil shock,when prices quadrupled,and 1979一1980,when they also almost tripled.Both previous shocks resulted in double-digit inflation and global economic decline.So where are the headlines warning of gloom and doom this time?The oil price was given another push up this week when Iraq suspended oil exports.Strengthening economic growth,at the same time as winter grips the northern hemisphere,could push the price higher still in the short term.Yet there are good reasons to expect the economic consequences now to be less severe than in the l970s.In most countries the cost of crude oil now accounts for a smaller share of the price of petrol than it did in the l970s.In Europe,taxes account for up to four-fifths of the retail price,so even quite big changes in the price of crude have a more muted effect on pump prices than in the past.Rich economies are also less dependent on oil than they were,and so less sensitive to swings in the oil price.Energy conservation,a shift to other fuels and a decline in the importance of heavy, energy-intensive industries have reduced oil consumption.Software,consultancy and mobile telephones use far less oil than steel or car production.For each dollar of GDP(inconstant prices)in rich economies now use nearly 50%less oil than in 1973.The OECD estimates in its latest Economic Outlook that,if oil prices averaged $22 a barrel for a full year,compared with$13 in 1998,this would increase the oil import bill in rich economies by only 0.25％～0.5%of GDP.That is less than one-quarter of the income loss in 1974 or 1980. On the other hand,oil-importing emerging economies一to which heavy industry has shifted一have become more energy-intensive,and so could be more seriously squeezed.One more reason not to lose sleep over the rise in oil prices is that,unlike the rises in the 1970s,it has not occurred against the background of general commodity-price inflation and global excess demand.A sizable portion of the world is only just emerging from economic decline.The Economist's commodity price index is broadly unchanging from a year ago.In 1973 commodity prices jumped by 70%,and in 1979 by almost 30%.The main reason for the latest rise of oil price is_______.A:global inflationB:reduction in supplyC:fast growth in economyD:Iraq's suspension of exports
Which two statements are true about terms in a routing policy?（）A、A routing policy cannot have more than one term.B、If a term does not contain a from statement, all routes match.C、If a term does not contain a from statement, the Junos OS will not commit.D、A then statement is not mandatory in a term.
Which statement about active and passive surveys is incorrect？（）A、Active mode does not require the client to be specifically confguredB、Passive mode can survey more than one access point at a timeC、Active mode yields signal-quality information such as packet retries and lost packetsD、Active mode requires more time to survey but yields more information results than passive mode does
单选题Advertisement: The most flavorful olives in the world are kalamata olives. The more kalamata olives used to make a bottle of olive oil, the more flavorful the oil, and no company buys more kalamata olives than Zorba’s Olive Oil. Therefore, when you buy Zorba’s Olive Oil, you’re buying the most flavorful olive oil available today. The reasoning presented in the advertisement is flawed because it overlooks the possibility that:ANot all of Zorba’s competitors use kalamata olives in their oil.BZorba’s sells more olive oil than any other company.CThe most flavorful olive oil is not necessarily the best olive oil.DBecause of bulk discounts, Zorba’s pays less per kilogram of kalamata olives than does its competitors.EThe number of kalamata olives harvested every year is far less than the number of Spanish olives harvested every year.
单选题（）is not a condition for a ship of 400 tons gross tonnage and above other than an oil tanker to discharge certain amount of oil or oily mixtures into the sea.Athe ship is not within a special areaBthe ship is more than 12 nautical miles from the nearest landCthe ship is proceeding en routeDthe instantaneous rate of discharge of oil content does not exceed 60 liters per nautical mile
单选题Which substance is NOT considered to be Oil under the pollution prevention regulations? （）APetroleum and fuel oilBSludgeCOil mixed with dredge spoilDOil refuse and oil mixed with wastes
单选题The vapors given off by heated fuel oil are flammable, explosive, and （）Alighter than airBheavier than airCodorlessDnontoxic
单选题What type of oil is not covered in the oil pollution law?（）Amineral oilBmachinery oil being transferred for shipboard useCcrude oil unrefinedDnormal bilge oil and water
单选题A refrigerant with oil in solution has a （）.Ahigher boiling temperature for a given pressure than does a pure refrigerantBlower boiling temperature for a given pressure than does a pure refrigerantCboiling pressure equal to that of a pure refrigerant at a given pressureDboiling point will not be affected by entrained oil
单选题Which of the following statements is true concerning an oil cooler?（）AThe oil temperature is less than the cooling water temperatureBThe oil pressure is less than the cooling water pressureCThe oil pressure is greater than the cooling water pressureDThe oil flow control valve is always installed in the oil input line
单选题Which statement is TRUE concerning gasoline vapors on board a vessel（）.AThey are heavier than air and will settle in the lowest part of the vesselBThey are lighter than air and will settle in the highest part of the vesselCThey should be vented into the engine to improve combustionDThey should be vented into the wheelhouse
问答题Practice 3 Energy-saving vehicles were part of the Green Transportation Festival in the US in 2003. The vehicles shown were designed to reduce America’s dependence on oil and help the environment. There are exhibits of cars and buses at the festivals. Most of them use little gas or use another kind of fuel such as natural gas. People are also urged to consider simpler ways of getting around, such as walking, biking and using public transportation systems. The United States has less than five per cent of the world’s population, but uses about twenty-five per cent of the world’s oil. More than half of the nation’s oil is imported. Most of it goes to transportation. Festival organizers said progress in technology was making it possible for Americans to reduce their dependence on oil. That is because the kinds of energy-saving vehicles are increasing. Efforts to reduce oil imports in the United States would also have important environmental benefits. The burning of oil as fuel is responsible for gases blamed for climate change. When gasoline is burned in cars, it also pollutes the air. This leads to many health problems.
单选题Which of the following conditions could be a cause of excessive fuel dilution of diesel engine lube oil?（）ALeaking fuel injectorsBLower than normal compressionCDelayed fuel injectionDAll of the above are correct
单选题Concerning the incinerator’s operation, which of the following is not correct?（）AScavenging time should be more 30 seconds before ignitingBThe temperature of sludge tank is 80~100℃CFirst igniting the incinerator with diesel oil, when the temperature of health is about 600℃, the sludge oil drawn inDThe ash can be dumped into sea when the distance is more than 3 miles from land
单选题When using a fuel with a higher than normal sulfur content in an auxiliary diesel engine, you should（）Amaintain higher than normal jacket water temperatureBchange the lube oil more frequently than normalCmaintain a higher air-box temperature than normalDmaintain a higher air-box pressure than normal