请教一道og11紫皮的题~

张大猴

以下是一篇文章节选的一小段~

Poliomyelitis，for example，emerged as an epidemic in the United States in the twentieth century by then，modern sanitation was able to delay exposure to polio Until adolescence or adulthood，at which time polio infection produced paralysis． Previously, infection had occurred during infancy, when it typically provided lifelong immunity without paralysis．Thus，the hygiene that helped prevent typhoid epidemics indirectly fostered a paralytic polio epidemic.

6. The passage suggests that a lack of modern sanitation would make which of the following most likely to occur?

(A)  An outbreak of Lyme disease

(B)  An outbreak of dengue hemorrhagic fever

(C)  An epidemic of typhoid

(D)  An epidemic of paralytic polio among infants

(E)  An epidemic of paralytic polio among adolescents and adults

一直没看明白~那位高人能帮忙分析一下~谢谢

张大猴

答案是C

张大猴

求助呀~

Joshwu

·“Polio” is a disease that will produce paralysis when it is infected in adulthood; however such infection in infancy will not result in paralysis as only infants can develop an immunity to the disease. Modern sanitation, intending to prevent typhoid epidemic, prevents the infection of “Polio” in infancy, and in turn cause the probability that people may infect the polio when they grow up.