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?
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.
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