2. 职称英语
  3. Since 1975 there has been in the United States a dramatic decline in the inciden

Since 1975 there has been in the United States a dramatic decline in the inciden

游客2025-02-26  24
问题 Since 1975 there has been in the United States a dramatic decline in the incidence of traditional childhood diseases such as measles. This decline has been accompanied by an increased incidence of Peterson’s disease, a hitherto rare viral infection, among children. Few adults, however, have been affected by the disease. Which of the following, if true, would best help to explain the increased incidence of Peterson s disease among children?
选项 A、Hereditary factors determine in part the degree to which a person is susceptible to the virus that causes Peterson’ s disease.
B、The decrease in traditional childhood diseases and the accompanying increase in Peterson’s disease have not been found in any other country.
C、Children who contract measles develop an immunity to the virus that causes Peterson s disease.
D、Persons who did not contract measles in childhood might contract measles in adulthood, in which case the consequences of the disease would generally be more severe.
E、Those who have contracted Peterson’s disease are at increased risk of contracting chicken pox.
答案 C
解析 正确答案应能解释麻疹发病率的下降和Peterson病发病率的上升。(C)指出得过麻疹的儿童形成了Peterson的免疫力，既然麻疹发病率少了，那么更少的儿童有对Peterson的免疫力，因此，随着前者的下降而后者上升，所以(C)正确；(A)指出遗传因素的作用，但并不能解释为什么Peterson发病率上升；(B)中的“其他任何国家”，与“美国”无关；(D)、(E)均不能起到解释作用.
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