阅读理解 Interferon For several years, scientists have been testing a substance called interferon (干扰素),a potential wonder drug that is proving to be effective in treating a variety of ailments, including virus infections, bacteria infections, and tumors. To date, the new drug has provoked no negative reaction of sufficient significance to discourage its use. But in spite of its success, last year only one gram was produced in the entire world. The reason for the scarcity lies in the structure of interferon. A species specific protein, the interferon produced from one animal species cannot be used in treating another animal species. In other words, to treat human beings, only interferon produced by human beings may be used. The drug is produced by infecting white blood cells with a virus. Fortunately, it is so potent that the amount given each patient per injection is very small. Unlike antibiotics(抗菌素), interferon does not attack germs directly. Instead, it makes unaffected cells resistant to infection, and prevents the multiplication of viruses within cells. As you might conclude, one of the most dramatic uses of interferon has been in the treatment of cancer. Dr. Hans Strander, research physician at Sweden''s famous Karolinska Institute, has treated more than one hundred cancer patients with the new drug. Among a group of selected patients who had undergone surgical procedures for advanced cancer, half were given conventional treatments and the other half were given interferon. The survival rate over a three-year period was 70 percent among those who were treated with interferon as compared with only 10 to 30 percent among those who had received the conventional treatments. In the United States, a large-scale project supported by the American Cancer Society is now underway. If the experiment is successful, interferon could become one of the greatest medical discoveries of our time.
单选题 Antibiotics kill germs by attacking them directly, while interferon does not.
【正确答案】 A
【答案解析】第三段有明确说明：Unlike ant，ibiotics，interferon does not attack germs directly．与抗菌素不同的是干扰素直接袭来病菌因此命题正确。
单选题 The effect interferon has on infection is that it keeps healthy cells from becoming infected.
【正确答案】 A
【答案解析】参见第三段第2句：…it(指interferon)makes unaffected cells resistant to infection干扰素能使未受感染的细胞防止感染，因此正确。
单选题 Interferon is produced by infecting viruses, bacteria, and tumors with a drug.
【正确答案】 B
【答案解析】在第2段第四句中提出：The drug(interferon)is produced by infecting white blood cells with a virus．干扰素是从带有病毒的被感染的白细胞中提炼出来的，故错误。
单选题 Interferon has not been widely used because it is still very dangerous.
【正确答案】 B
【答案解析】文中讲到干扰素在治疗病毒感染、细菌感染以及肿瘤的疾病时是一种神奇的药物，然而全世界去年却只产出一克，这说明生产干扰素是相当困难的，因此命题错误。
单选题 The result of Dr. Stranders experiments with interferon is that 70 percent among patients who were treated with interferon survived.
【正确答案】 A
【答案解析】对干扰素实验结果是The survival rate…was 70 percent…who were treated with interferon…only 10 to 30 percent…who had received the conventional treatments．(第四段最后一句)实验在一百名患有癌症的病人中进行。一半病人接受了干扰素的治疗，三年间有70％的病人存活下来，另一半人接受常规治疗，只有10％-30％的病人存活下来，因此命题正确。
单选题 21 Interferon causes healthy cells to grow.
【正确答案】 C
【答案解析】从文章内容可知该命题未涉及。
单选题 Interferon has serious side effects, whereas antibiotics do not.
【正确答案】 B
【答案解析】干扰素有极大的副作用，而抗菌素却没有，这显然不符合事实，因此命题错误。