GMAT-20-5请教求解思路

sv2000

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?

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yangsh

c

deanjiang

up

steveyangxt

取非