Many important types of medicine have been developed from substances discovered in plants that grow only in tropical ...

SamA on October 8, 2019

Hello @Meredith,

The problem with E is that it is basically a restatement of the conclusion. It doesn't give us any new information to work with. Also, the passage does not mention what should or should not happen. The conclusion simply states that if the forests are not preserved, then important medicine won't be developed. The argument does not depend on what we should or should not do.

A required assumption is something that is not stated in the passage, but the argument depends on its truth. We need something that fixes a hole in the argument, or defends the argument from attacks. Answer choice A is correct because it does the latter.

Even if unstudied plants remain in the forest, what if we've already gathered every possible medicinal substance from the plants we have studied?

This attacks the argument because, while the plants may be unknown, the substances they contain might be already known. Therefore, destruction of the forests would not prevent development of medicine, which contradicts the conclusion. Assumption A defends against this attack. If we assume that there are undiscovered substances remaining in the forest, then the argument stands.