【正文】 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 正確答案是 27. The stress man39。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. 正確答案是 22. The passage implies that the first testtube babies were born in ______. A) Canada B) Britain C) America D) Australia 正確答案是 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. 正確答案是 24. According to the passage, which of the following is NOT mentioned? A) People are not sure of the reason why 。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。ve ever been pregnant yourself, one thing is certain: You wonder what it39。t digest the huskless rice B) proved beriberi is transmitted by germs C) were later cooked for the patients39。beriberi39。. Quite a number of such substances are known and they are given letters to identify them, A, B, C, D, and so on. Different diseases are associated with deficiencies of particular vitamins. The vitamins necessary for a healthy body are normally supplied by a good mixed diet, including a variety of fruit and green vegetables. It is only when people try to live on a very restricted diet, say during extended periods of religious fasting, or when trying to lose weight, that it is necessary to make special provision to supply the missing vitamins. One example of the dangers of a restricted diet may be seen in the disease known as beriberi, which used to afflict large numbers of Eastern peoples who lived mainly on rice. In the early years of this century, a Dutch scientist called Eijkman was trying to discover the cause of beriberi. At first he thought it was transmitted by a germ. He was working in a Japanese hospital, where the patients were fed on rice which had had the outer husk removed from the grain. It was thought this would be easier for weak, sick people to digest. Eijkman thought his germ theory was confirmed when he noticed, the chickens in the hospital yard, which were fed on scraps from the patients39。s success. Starting next year, the foundation will paint chevrons and other patterns of stripes on selected roads around the country to test how well the patterns reduce highway crashes. Excessive speed plays a major role in as much as one fifth of all fatal traffic accidents, according to the foundation. To help reduce those accidents, the foundation will conduct its tests in areas where speedrelated hazards are the greatest curves, exit slopes, traffic circles, and bridges. Some studies suggest that straight, horizontal bars painted across roads can initially cut the average speed of drivers in half. However, traffic often returns to full speed within months as drivers bee used to seeing the painted bars. Chevrons, scientists say, not only give drivers the impression that they are driving faster than they really are but also make a lane appear to be narrower. The result is a longer lasting reduction in highway speed and the number of traffic accidents. 6. The passage mainly discusses ______. A) a new way of highway speed control B) a new pattern for painting highways C) a new approach to training drivers D) a new type of optical illusion 正確答案是 7. On roads painted with chevrons, drivers tend to feel that ______. A) they could avoid speedrelated hazards B) they are driving in the wrong lane C) they should slow down their speed D) they are approaching the speed limit 正確答案是 8. The advantage of chevrons over straight, horizontal b