GMAT Critical Reasoning (CR) | Exposure to certain chemicals commonly used in elementary

Hi,

I have stuck on this question. I read posts, but still I couldn't get why the answer is C

This is how i understand the argument:
Premise: Exposure to chemicals --> causes allergic reaction in children
Premise: Nurses report that number of children sent to them for chemical allergy treatment has increased over the past ten years
Conclusion: Children have been exposed to greater amount of chemicals or children are more sensitive than children 10 years ago.

As derived from conlcusion: