Sofar,howlonghastheShanghaiWorldExpobeenon?A.For20days.B.Foramonth.C.Forfourweeks.D.Forabout50days.
Sofar,howlonghastheShanghaiWorldExpobeenon?
A.For20days.
B.Foramonth.
C.Forfourweeks.
D.Forabout50days.
相关考题：
共用题干Black Holes1 Black holes can be best described as a sort of vacuum,sucking up everything in space.Scientists have discovered that black holes come from an explosion of huge stars.Stars that are near death can no longer burn due to loss of fuel , and because its temperature can no longer control the gravitational（重力的）force,hydrogen ends up putting pressure onto the star's surface until it suddenly explodes then collapses.2 Black holes come from stars ihat are made of hydrogen,other gases and a few metals.When these explode it can turn into a stellar-mass（恒星质量) black hole , which can only occur if the star is large enough (should be bigger than the sun)for the explosion to break it into pieces,and the gravity starts to compact every piece into the tiniest particle.Try to see and compare:if a star that's ten times the size of the sun ends up being a black hole that's no longer than 70 kilometers,then the Earth would become a black hole that'S only a fraction of an inch!3 Objects that get sucked in a black hole will always remain there,never to break free.i1it remember that black holes can only gobble up（吞噬）objects within a specific distance to it.It's possible for a large star near the sun to become a black hole,but the sun will continue to stay in place.Orbits（轨道）do not change because the newly formed black hole contains exactly the same amount of mass as when it was a star, only this time its mass is totally contracted that it can end up as no bigger than a state.4 Sofar,astronomers have figured out that black holes exist because of Albert Einstcin's theory of relativity.In the end,through numerous studies,they have discovered that black holes truly exist.Since black holes trap light and do not give off light,it is nearly impossible to detect black holes via a telescope.But astronomers continue to study galaxies（银河系）, space and the solar system to understand how black holes might evolve.It is possible that black holes can exist for millions of years,and later contribute to a bigger process in galaxies,which can eventually lead to creation of new entities（实体）.Scientists also credit black holes as helpful in learning how galaxies began to form.When a large star explodes,the gravity compacts every piece into______.A:the existence of black holesB:the creation of new entitiesC:the same amount of massD:an fraction of an inchE:a fraction of an inchF:the tiniest particle
共用题干Chest Compressions:Most Important of CPRCardiopulmonary resuscitation,or CPR,can save the life of someone whose heart has stopped .The condition is called cardiac arrest. The heart stops pumping blood. The person stops breathing. Without lifesaving measures,the brain starts to die within four to six minutes.CPR combines breathing into the victim's mouth and repeated presses on the chest.______(46).However,a new Japanese study questions the usefulness of mouth-to-mouth breathing. The study was published in the British medical magazine,The Lancet. Doctors in Tokyo led the re- search .It examined more than four thousand people who had suffered cardiac arrest. In all the cases,witnesses saw the event happen.More than one thousand of the victims received some kind of medical assistance from witnes- ses .Seven hundred and twelve received CPR.Four hundred and thirty-nine received chest pres- ses only.______(47)The researchers say any kind of CPR improved chances of the patient's survival. But,they said those people treated with only chest presses suffered less brain damage. Twenty-two percent survived with good brain ability.______(48).The American Heart Association changed its guidelines for CPR chest presses in 2005.______(49)Gordon Ewy is a heart doctor at the University of Arizona College of Medicine in Tucson. He wrote a report that appeared with the study.Doctor Ewy thinks the CPR guidelines should be changed again.He said the heart association should remove rescue breaths from the guidelines. He argues that more witnesses to cardiac arrests would provide treatment if rescue breaths are not a part of CPR. He says this would save lives______(50).Cardiac arrest kills more than 300,000 people in the United States every year. The American Heart Association says about ninety-five percent of victims die before they get to a medical center.______(46)A: Sofar,we have not known exactly yet whether mouth-to-mouth breathing is really useless in CPR.B: Only ten percent of the victims treated with traditional CPR survived with good brain a-bility.C: CPR keeps blood and oxygen flowing to the heart and brain.D: His studies show that many people do not want to perform mouth-to-mouth breathing on a stranger for fear of getting a disease.E: It said people should increase the number of chest presses from fifteen to thirty for every two breaths given.F: No mouth-to-mouth rescue breaths were given to them.