Unit 3 Computers Learning about language课时作业

第一节 完形填空

　　In an ideal world, people would not perform experiments on animals. For the people, they are expensive. For the animals, they are stressful and often painful. That ideal world, 1 ,is still some way away. People need new drugs and vaccines. They want 2 from the toxicity (毒性)of chemicals. The search for basic scientific answers goes on. 3 the European Commission is moving ahead with proposals that will 4 the number of animal experiments carried out in the European Union, by requiring toxicity tests on every chemical 5 for use within the union's borders in the past 25 years.

　　Already, the commission has 6 10,000 chemicals that have not yet been tested. It wants 30,000 of these to be examined right away, and plans to spend between $ billion -$ 8 billion doing so. The number of animals used for toxicity testing in Europe will thus, experts reckon, quintuple (翻五倍）from just over 1 million a year to about 5 , unless they are saved by some dramatic 7 in non-animal testing technology. Animal experimentation will therefore be around for some time yet. But the search for substitutes continues.

　　A good place to start finding 8 for toxicity tests is the liver-the organ responsible for breaking toxic chemicals down into safer molecules that can then be eliminated from body. Two firms, one large and one small, told the meeting how they were using human liver cells removed incidentally during surgery to test various substances for long-term toxic effects.

　　PrimeCyte, the small firm, grows its cells in cultures(士音养基）over a few weeks and doses them regularly with the substance under 9 . The characteristics of the cells are carefully10 ,to look for changes in their microanatomy(组织学). Pfizer, the big firm, also doses its cultures regularly, but rather than studying 11 cells in detail, it counts cell numbers. If the number of cells in a culture changes after a sample is added, that suggests the chemical 12 is bad for the liver.

Other tissues, too, can be tested 13 of animals. Epithelix, a small firm in Geneva, has developed an 14 version of the lining of the lungs. According to Huang Song, one of Epithelix's researchers, the firm's cultured cells have similar microanatomy to those found in natural lung linings, and 15 in the same way to various chemical messengers. Dr. Huang says that they could be used in long-term toxicity tests of airborne chemicals and could also help identify treatments for lung diseases.

　　All this suggests that though there is still some way to go before drugs, vaccines and other substances can be tested routinely on cells rather than live animals, useful progress is being made.

1. A. fortunately B. sadly C. ironically D. technically

2. A. protection B, identification C. isolation D. interaction

3. A. However B. Indeed C. Instead D. Furthermore

4. A, increase B. decrease C. prohibit D. specify

5.A. tested B. created C. assessed D.approved

6. A. outlined B. imposed C. identified D.released

7. A. diagnoses B. advances C. proofs D.appearances

8. A. alternatives B. breakthroughs C. possibilites D. implications

9.A. suspicion B. control C. way D.investigation

10.A. monitored B. studied C analyzed D.classified