单选题 According to the text; virgin-soil epidemics can be distinguished from other catastrophic outbreaks of disease in that virgin-soil epidemics

A、 recur more frequently than chronic diseases.
B、 involve populations with no prior exposure to a disease.
C、 usually involve a number of interacting diseases.
D、 are less responsive to medical treatment than are other diseases.

【正确答案】 B

【答案解析】[注释] 细节理解题。本题问：根据本文，处女地流行病与发生其他灾难性疾病的区别是什么?第2段第1句写道：“处女地流行病是指处于危险中的人过去从未接触过的袭击他们的疾病，因而几乎没有免疫防御力，”选项[B]“(处女地流行病)使过去从未接触过某种疾病的人受感染”与第2段第1句的意思相一致，故应选[B]。注意：involve sb．with sth．使某人与某事接触、打交道，involve sb．in sth．表明某人与某事有关联；The witness's statement involves you in the robbery．(证人的证词表明你与抢劫案有关联。)