Why A?

Could you please explain why A is correct?

@joshuavt, the conclusion of the argument is that in "most" of this forest, the moth outbreak should not be stopped. The premise is that moth outbreaks are beneficial to forests that are unnaturally crowded with immature trees. So to go from "moth outbreaks are beneficial in certain circumstances" to "we shouldn't stop this moth outbreak in most of this particular forest" requires evidence that "most of this particular forest" meets the conditions in which a moth outbreak would be beneficial. (A) provides this by saying that "more than half (most) of the forest is unnaturally crowded with immature trees" and would therefore benefit from the moth outbreak.

Thank you!

Can you explain to me why answer choice C would be wrong in this scenario?