C. It is based on existing technology.

　　D. Carbon dioxide Can be converted into fuel

　　答案：D

　　37. What is the biggest problem with hydrogen-powered cars？

　　A.There is no cheap source of hydrogen.

　　B. There might be a safety problem in hydrogen production.

　　C.They may still be a cause of global warming.

　　D.They are not suitable for long-distance travel.

　　答案：C

　　38.If what is proposed by the two scientists becomes true,___________________.

　　A.air pollution will，become a thing of the past

　　B.there will be no need for gasoline substitutes

　　C. people will be able to use much cheaper engergy

　　D.there will be no more biofuel-powered vehicles

　　答案：B

　　39. Which of the following Call best describe the attitude of Martin I Hoffert to the proposal?

　　A.Indifferent. B. Positive. C.Suspicious.D.Critical.

　　答案：B

　　40. The passage is mainly written to________________。

　　A. introduce a new concept

　　B.compare different energy sources

　　C.stress the importance ofgasoline

　　D.discuSS solutions tO global warming

　　答案：A

　　Passage Three

　　In her international bestselling Talk to the Hand,author Lynne Truss.argues that common courtesies such as saying“Excuse me”are practically extinct.There are certainly plenty who would agree with her.

　　Is it really true?We decided to find out by experiments.In dozens of American cities,our reporters performed two experim6rits：“door tests”(would anyone hold one open for them?)；and“document drops”(who-would help them retrieve a pile of“accidentally”dropped papers?).Along the way,the reporters encountered all types：men and women of different races,ages，professions,and income levels.

　　While 90 percent of the people passed the door test，only 55 percent passed the document drop.Are people less likely to help others when doing so takes extra effort or time? Not always，he reporters found.Take the pregnant woman who thought nothing of bending down to help us with our papers.Or the woman named Liz who balanced two coffees，her keys and her wallet on a takeout tray with one hand，while picking up papers off the wet pavement with the other.Her reason for helping?“I was there,”she said.

　　Overall，men were the most willing to help，especially when it came to document drops.In those，men offered aid 63 percent of the time，compared to 47 percent among women.Of course，men weren’t entirely democratic about whom they’d help.All of them held the door for the female reporter,and were more than twice as likely to help her pick up fallen papers than they were to help our male reporter.

　　By far,the most common reason people cited for being willing to go out of their way to help others was their upbringing.“It’S the way I was raised，”said one young woman who held a door open despite struggling with her umbrella on a rainy day in Brooklyn.