为了避免戊型肝炎的流行，血液中心将立即开始筛选所有的献血者。尽管新的筛选测试估计将从献血者中筛选掉5%，却仍然会放过三分之二的戊型肝炎携带者。因此，大约10%的献血者将仍然提供带有戊型肝炎病菌的血液。 上面的推论基于以下哪项假设
A．在大量的案例中，携带戊型肝炎的献血者并不会发病
B．对被戊型肝炎测试筛选下来的献血者数字的估计是被低估了的
C．在大量的案例中，携带戊型肝炎病菌的献血者并没有携带其它常规测试能够筛选出来的相关病菌
D．在想要献血的人中，戊型肝炎患者的比例比在整个人口中的比例要低
参考答案：C
解析： 前提型题目。题干论据为“医院在筛选掉5%的献血者后，仍然会放过三分之二的戊型肝炎携带者”，推论是：仍有10%的献血者为戊型肝炎携带者。C项是必须的假设，因为携带戊型肝炎病菌的人不能够被其他常规测试筛查出来，才能得出被放过的戊型肝炎病菌携带者为10%；其他各项都不是必须的假设。
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| It seems that the cities in the future will have to change. Because the world's population __1__ , there will be __2__ people in the cities tomorrow. It may be __3__ for any family to live in a house with land around it. There__4__ enough space for them. __5__ to solve this problem may be the skyscraper city (摩天城). The highest building in the world  today is in Taipei. It's about 509 metres high. The skyscraper cities in the future will be many times __6__ . In a skyscraper city about 250,000 people will live. Nearly a million people can __7__ in four of these great buildings. Each skyscraper city will have four towns in it and each town will have ten villages. They will live, work and __8__ their free time in them. They won't need to leave the city __9__ they want to. They will be able to move about in the city by transport controlled __10__ computers. Let's imagine how the life will be then! | |||
| ( ) 1. A. has grown ( ) 2. A. many ( ) 3. A. impossible ( ) 4 A. aren't ( ) 5. A. A way ( ) 6. A. lower ( ) 7. A. live ( ) 8. A. spend ( ) 9. A. until ( ) 10. A. by | B. is growing B. much B. possible B. won't be B. A road B. shorter B. study B. cost B. when B. at | C. are growing C. more C. important C. won't have C. An answer C. taller C. work C. pay C. while C. with | D. have grown D. larger D. necessary D. haven't D. An idea D. higher D. be D. take D. unless D. in |