Exposure
to certain chemicals commonly used in elementary schools as cleaners or pesticides
causes allergic reactions in some children.
Elementary school nurses in Renston report that the proportion of
schoolchildren sent to them for treatment of allergic reactions to those
chemicals has increased significantly over the past ten years.
Therefore, either Renston’s schoolchildren
have been exposed to greater quantities of the chemicals, or they are more
sensitive to them than schoolchildren were ten years ago.

Which
of the following is an assumption on which the argument depends?

B     Children who are
     allergic to the chemicals are no more likely than other children to have
     allergies to other substances.

C     Children who
     have allergic reactions to the chemicals are not more likely to be sent to
     a school nurse now than they were ten years ago.

D     The chemicals
     are not commonly used as cleaners or pesticides in houses and apartment
     buildings in Renston.

E      Children
     attending elementary school do not make up a larger proportion of
     Renston’s population now than they did ten years ago.    這題答案是C,請問B錯在哪?C又對在哪?