大学英语四级考试练习(编辑修改稿)

大学英语四级考试练习(编辑修改稿)内容摘要：

20. The ingredient missing from milled rice ______. A) was vitamin B B) did not affect the chickens C) was named the Eijkman vitamin D) has never been accurately identified 正确答案是 Passage 5 The idea of testtube babies may make you starryeyed with delight at the wonders of modern medicine or blearyeyed with considering the moral/legal implications of starting life in a laboratory. But if you39。 ve ever been pregnant yourself, one thing is certain: You wonder what it39。 s like to carry, a test tube baby. Are these pregnancies normal Are the babies normal The earliest answers came from Australia, where a group of medical experts at the Queen Victoria Medical Center in Melbourne took a look at the continent39。 s first nine successful testtube pregnancies. The Australians report that the pregnancies themselves seemed to proceed according to the plan, but at birth some unusual trends did show up. Seven of the nine babies turned out to be girls. Six of the nine were delivered by Caesarean section. And one baby, a twin, was born with a serious heart defect and a few days later developed lifethreatening abdominal problems. What does it all mean Even the doctors don39。 t know for sure because the numbers are so small. The proportion of girls to boys is high, but until there are many more testtube babies no one will know whether that39。 s pure coincidence or something special. The same thing is true of the single heart defects it usually shows up in only 15 out of 60,000 births in that part of Australia, but the fact that it occurred in one out of nine testtube babies does not necessarily mean that they are at special risk. One thing the doctors can explain is the high number of Caesareans. The Australian researchers report that they are quite encouraged. All the babies are now making normal progress even the twin with the birth defects. 21. Which of the following would be the most appropriate title for the passage? A) The proportion of Testtube Girls to Boys, B) Are Testtube Babies Healthy C) The Social Meaning of the Idea of Testtube Babies. D) The Moral Issue Associated with Testtube Babies. 正确答案是 22. The passage implies that the first testtube babies were born in ______. A) Canada B) Britain C) America D) Australia 正确答案是 23. Which of the following statements best describes the anization of the passage? A) A problem is examined and possible reasons and solutions are given. B) A procedure is explained and its importance is emphasized. C) Two contrasting views of a problem are presented. D) Recent scientific advancements are outlined in order of importance. 正确答案是 24. According to the passage, which of the following is NOT mentioned? A) People are not sure of the reason why。 the proportion of testtube girls to boys is high. B) Heart defect usually occurs in only 15 out of 60,000 in Australia. C) Heart defect shows up in one out of nine testtube babies. D) The testtube babies are growing well. 正确答案是 25. Where did the passage most probably appear? A) In a specialized publication for moral philosophers. B) In a specialized report for doctors. C) In a weekly news magazine with a large readership. D) On the front page of a daily newspaper. 正确答案是 Passage 6 There are two main things that make aircraft engineering difficult: the need to make every ponent as reliable as possible and the need to build everything as light as possible. The fact that an aeroplane is up in the air and cannot stop if anything goes wrong, makes it perhaps a matter of life or death that its performance is absolutely dependable. Given a certain power of engine, and consequently a certain fuel consumption, there is a practical limit to the total weight of aircraft that can be made to fly. Out of that weight as much as possible is wanted for fuel, radio navigational instruments, passenger seats, or freight room, and, of course, the passengers or freight themselves. So the structure of the aircraft has to be as small and light as safety and efficiency will allow. The designer must calculate the normal load that each part will bear. This specialist is called the stress man. He takes account of any unusual stress that may be put on the part as a precaution against errors in manufacture, accidental damage, etc. The stress man39。 s calculations go to the designer of the part, and he must make it as strong as the stress man says is necessary. One or two samples are always tested to prove that they are as strong as the designer intended. Each separate part is tested, then a whole assembly for example, a plete wing, and finally the whole aeroplane. When a new type of aeroplane is being made, normally only one of the first three made will be flown. Two will be destroyed on the ground in structural tests. The third one will be tested in the air. When a plane has passed all the tests it can get a government certificate of airworthiness, without which it is illegal to fly, except for test flying. Making the working parts reliable is as difficult as making the structure strong enough. The flying controls, the electrical equipment, the fire precautions, etc. must not only be light in weight, but must work both at high altitudes where the temperature may be below freezing point and in the hot air of an airfield in the tropics. To solve all these problems the aircraft industry has a large number of research workers, with elaborate laboratories and test houses, and new materials to give the best strength in relation to weight are constantly being tested. 26. The two main requirements of aircraft design are ______. A) speed and cheapness B) reliability and passenger fort C) making things both light and dependable D) ability to stay up in the air and avoid breakdowns 正确答案是 27. The stress man39。 s job is to calculate ______. A) how safe the plane is B) how strong each part must be。