Investigators have not yet _______ the cause of the air crash. A. determinedB. exploredC. devisedD. hastened
Investigators have not yet _______ the cause of the air crash.
A. determined
B. explored
C. devised
D. hastened
相关考题：
Have they decided on the ______ of the new building yet? A. locateB. localC. locatedD. location
I _____my breakfast at 8, but_____ I lunch yet. .A. had, haven't hadB. had, didn't haveC. have had, didn't have
We ( ) on it for many hours but we have not yet reached any conclusion. A、have had workedB、have been workingC、are workingD、work
Air pollutionPeople and air pollution are often in the same places. This means that cities with large populations have the biggest problem of dirty air. Air pollution is caused by many different things. A major kind of air pollution is the gas from cars. Statistics(统计资料) show that 93 percent of all auto trips are within cities.Another major kind of dirty air is the burning of coal and oil for energy. This energy is needed to make electricity. Of course, much more electricity is used in the city than in the county.On the average, we throw away more rubbish than the year before. The burning of rubbish makes air pollution even worse. Many major industries are also responsible for the dirty air in the around cities. The fumes(烟)from iron, steel, chemical, and petrol production add particles(微粒)to the air.The effects of air pollution range from mild headaches to death. The levels of pollution found in heavy traffic may cause headaches for loss of clear vision. Wherever coal and oil are used for fuel, fumes may kill trees and plants and cause metal to corrode(腐蚀). In some of the larger cities, these fumes endanger the lives of human beings by contributing to lung diseases and causing early death.26. The key point of the passage is that().A. the cause of air pollution is peopleB. the causes and the effects of air pollution are both found in citiesC. the effects of air pollution range from headaches to death27. What is the purpose of this passage?A. to persuade people to stop polluting the air().B. to tell the causes of air pollutionC. to tell why cities are bad places to live28. Why is air pollution more grave in the city than in the country?().A. Because there are larger populations in cities.B. Because the air in the city is dirty.C. Because there are much more gas fumes from cars and burning of coal and oil for energy in the city than in the country.29. The fumes from coal and oil may cause metal().A. to corrodeB. to twistC. to turn black30. In larger cities, the fumes from coal and oil may contribute to().A. heart diseaseB. loss of clear visionC. lung diseases
If the engine does start on air, but combustion does not immediately begin, the cause may be _____.A.failure of the fuel pumpsB.starting air pressure too lowC.stop valve in air line closedD.the turning gear still engaged
What is the most probable cause of reduced capacity in a reciprocating air compressor ________．A.Carbon on cylinder headsB.Faulty unloaderC.Leaking air valvesD.Plugged air cooler
__________enough time and money, the investigators would have been able to discover more evidence in this case.A．GivingB．GivenC．To give D．Being given
If headaches only occur at night,lack of fresh air is often the cause.A:start B:begin C:happen D:visit
If headaches only occur at night,lack of fresh air is often the cause.A:start B:begin C:happen D:visit
单选题Broken valve strips in an operating low pressure, air compressor will cause （）.Aan immediate crankcase explosionBoil contamination in the compressed airCa decrease in compressor capacityDno immediate loss of the compressed air capacity
单选题The text suggests that investigators of monkeys’ social behavior have been especially interested in aggressive behavior among monkeys because ______.Aaggression is the most common social behavior among monkeysBsuccessful competition for incentives determines the social order in a monkey groupCsituation that elicit aggressive behavior can be studied in a laboratoryDmost monkeys are potentially aggressive, yet they live in social units that could not function without control of their aggressive impulses
单选题Air bubbles in a hydraulic governor can cause （）Asluggish responseBspeed droop variationsCisochronous governingDsensitivity increase
单选题Which of the following may cause that an engine doesnt turn on starting air?（）Atoo low starting air pressureBmain starting valve closedCneither A nor BDA and B
单选题Which cause of the following can lead to the engine not to start on air?（）Astarting air pressure too highBcorrect timing of starting air valvesCthree of the starting valves stuckDthe turning gear disengaged
单选题Which of the following problems could cause air to blow out through the inlet air filter of a running compressor?（）AExcessive compression in the cylinderBA broken intake valveCA dirty inlet filter elementDAn improperly adjusted discharge valve
单选题If over a period of weeks the air-box pressure of a turbo-charged, diesel engine, operating at full load, appears to be dropping off, the cause can be （）.Aopen air-box drainsBloss of cooling water to the diffuserCgradual fouling of the air filtersDimproperly timed exhaust valves
单选题_____AMany people died in a fire.BTwo persons were injured.CThere was a traffic accident.DThere was an air crash.
单选题In context, which version of the underlined part of sentence 3 (reproduced below) is the best?Baby lobsters are preyed on by fish and crabs because they don't have a hard shell yet and can't defend themselves with fierce claws yet.Athe lobsters still lack both hard shells and fierce claws with which to fend off predatorBthe lobsters cannot attack their fish and crab predators with fierce claws or fend their predators off with a hard shellCthey don't have a hard shell yet and can't defend themselves with fierce claws yetDthe lobsters don't have a hard shell and can't yet defend themselves with fierce clawsEthe fish and crabs do not have hard shells or fierce claws yet
单选题Exhaust temperature increases in all cylinders, the possible cause may be（） (1) increased scavenging air temperature (2) air in fuel pumps and fuel valves (3) fouling of air and gas passagesA(1)+(2)B(1)+(3)C(2)+(3)D(1)+(2)+(3)
单选题Disastrous explosions have been caused by accumulations of oil or oil vapour in air lines not drainedAccording to the above sentence, which of the following statements is true?（）AOil vapour in air piping are dangerousBExplosion will cause oil vapouring in air linesCOil vapour in air piping should be drainedDOil in air piping should not be drained
单选题When starting air is admitted, a diesel engine turns over very slowly without firingThe cause may be （）Aan obstruction in an cylinderBwater accumulation in some engine cylindersClow starting air pressureDlow scavenge air pressure
单选题Unless the conservator can find a way to protect the photographs in the archives from light and air, these precious historical documents have deteriorated and will continue to do so both in color and in fine detail.Ahave deteriorated and will continue to do soBwill continue to deteriorateChave been and will continue to deteriorateDwill continue to deteriorate, as they already have,Ewill be deteriorating yet more
单选题If the engine does start on air, but combustion does not immediately begin, the cause may be （）.Afailure of the fuel pumpsBstarting air pressure too lowCstop valve in air line closedDthe turning gear still engaged