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.

 参考答案是E。我觉得不对，应为题目说will increase significantly within the next few years，可是E最多也就是说最近打疫苗的会比较多。我觉得B挺好的。请高手指点。谢谢

E限定了时间，2-5年内一定会发生

所以可以确定注射疫苗的时间

SUPPORT

原文大意：

因为——疫苗昂贵；

        疫苗不容易把握注射时间；

        导致不使用疫苗；

所以——如果要使用疫苗，

答案就在这个所以的下半句话中，也就是，如果要使用疫苗，就要否定“两个因为"其中之一，即要么说“疫苗便宜了”，要么说“疫苗的注射时间可以把握”。

E的意思是：研究表明，在发生疫情的2-5个月之前，会有一种非常明显的气候征兆出现。也就是说，人们只要看到这个气候出现，就可以预测疫情将会在2个月以后到来。那么就可以准确把握注射疫苗的时间了。

B的意思是，其他国家不进口生病牛。这跟使不使用疫苗有啥关系？