Outbreaks of Rift Valley fever occur irregularly in East Africa, several years apart.When outbreaks do occur, they kill thousands of cattle. A livestock vaccine against the disease exists but is rarely used.It is too expensive for farmers to use routinely, and since it is not effective until a month after vaccination, administering it after an outbreak begins helps very little.Nevertheless, experts predict that use of the vaccine will increase significantly within the next few years.
Which of the following, if true, provides the strongest justification for the experts’ prediction?
A.Rift Valley fever is spread by mosquitoes, but each outbreak is so widespread that it is impractical to control it by using insecticides. B.When an outbreak of Rift Valley fever occurs, unaffected countries often refuse to import livestock from the countries affected by the outbreak. C.It would take less than a month for producers of the vaccine to adjust their production operations to cope with a large increase in demand. D.Many cattle farmers in East Africa are nomadic or live in remote villages, and such farmers, who have little access to modern veterinary medicine, are particularly hard hit by outbreaks of Rift Valley fever. E.Recently published research has shown that certain identifiable climatic conditions are almost invariably followed, within two to five months, by an outbreak of Rift Valley fever.
答案E 前人帖子都查過了 我選B 原因是 其他國家不進口感染的R地區牲畜 那麼R就會不管疫苗價格 大量買疫苗注射牲畜 完全可以支持結論呀 作者: 切尔西 时间: 2010-4-22 14:57
题目中的主要原因是since it is not effective until a month after vaccination, administering it after an outbreak begins helps very little，而那些人预测说这些疫苗会被大量采用，所以应该找出一个原因来削弱这个原因，这里E最佳，B中虽然说其他国家不进口这些被感染的牲畜，但是如果这个疫苗不起作用的话，就算用了那些牲畜也还是会感染病毒哈，那样的话那些不进口的国家仍然会不进口，所以B无法支持题目的预言呢作者: 冬眠的橙子 时间: 2016-4-11 23:14
我觉得可能是因为B选项无法削弱原题的逻辑~就算别国不愿意买，疫苗对他们来说还是很贵&不能控制疫情，那么疫苗的使用不一定会显著增加吧~