20-119
Scientists have discovered the importance of social and ecological factors to epidemics. Polimyelitis, for example, emerged as an epidemic in the United States in the twentieth centry; by then moder sanitation was able to delay exposure to polio untill adolescence or adulthood, at which time polio infection produced paralysis. Previously, infection had occured during infancy, when it typically provided lifelong immunity without paralysis. Thus the hygiene that helped prevent typhoid epidemics indirectly fostered a paralytic polio epidemic.
119. The passage suggests that a lack of modern sanitation would make which of the following most likely to occur?
C an epidemic of typhoid
D an epidemic of paralytic polio among infants
E an epidemic of paralytic polio amnong adolesents and adults.
(D) because the context mentions: Previously, infection had occured during infancy, when it typically provided lifelong immunity without paralysis. As a result, (D) won't be correct.
also, according the above condition, the infants already got the immunity. then the adults and adolescents won't get the epidemic either.作者: EGHJUYMN 时间: 2010-5-13 21:16
回答此题还是从原文出发。
Thus the hygiene that helped prevent typhoid epidemics indirectly fostered a paralytic polio epidemic.--->hygiene prevented typhoid epidemics.
如果没有了hygiene ，那么typhoid epidemics就会occur.作者: rosswye 时间: 2010-5-14 06:41
看来，还是要关注原文细节的啊。作者: sumerlaws 时间: 2010-5-14 21:59
moder sanitation was able to delay exposure to polio untill adolescence or adulthood, at which time polio infection produced paralysis.
