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

Mehran on May 7, 2018

Hi @a42, thanks for your post.

This is a Strengthen with Necessary Premise question. The stimulus here presents an argument, the conclusion of which is "If the tropical rain forests are not preserved, important types of medicine will never be developed."

The stimulus tells us that (a) many important types of medicine have been developed from substances discovered in plants that grow only in tropical rain forests, and (b) there are thousands of plant species in these rain forests that have not yet been studied by scientists. It further states (c) it is very likely that many such plants also contain substances of medicinal value.

The necessary assumption is stated in (A): "there are substances of medicinal value contained in tropical rain forest plants not yet studied by scientists that differ from those substances already discovered in tropical rain forest plants."

If you negate this: none of the substances of medicinal value contained in the tropical rain forest plants not yet studied by scientists differ from those already discovered.

If that is true, the argument in the stimulus falls apart.

Answer choice (D) is incorrect because it says "if those species are studied by scientists." But the conclusion of the stimulus explains that such study is impossible "if the tropical rain forests are not preserved." In other words, answer choice (D) is irrelevant because it posits a hypothetical at odds with the argument we are tasked with strengthening.

Hope this helps! Please let us know if you have any additional questions.