标题: 求解一道传染病与疫苗的防治问题 [打印本页] 作者: Helloface 时间: 2010-9-27 13:27 标题: 求解一道传染病与疫苗的防治问题 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. 求助答案为何是E?我选的A~~~~~~~ 选E是因为气候不好导致传染病蔓延么？？那A明确说蚊子传播了呀，虽然最后的杀虫剂或许有些无关，但是E也没有明确说气候环境导致传染病爆发后还有继续~~~想不清楚了- -作者: Carrie2009 时间: 2010-9-27 14:38
我觉得A不好，因为A说杀虫剂impractical, 不等于vaccination就practical。 B 的unaffected countries 与题目无关 C 本题与花多久检验vaccine 无关 D 无关 E 虽然看起来也不太好，但是它的“within two to five months” 可以在时间上支持使用vaccine。再者，题中最后说“next few years”，E说“ almost invariably followed”，刚好说明一种常态。