How will the right answer fit in terms of support and conclusion?

Only the right answer will complete the conclusion supported by the passage.

Highlight the main conclusion in the passage, if there is one:

Only the beginning of the conclusion is in there. The right answer will fill in the conclusion about the “use of these pesticides”.

Although [BACKGROUND], studies have shown clearly that [SUPPORT]. [CONCLUSION].

Map the wording of the answers to the wording of the passage:

(A) is uneconomic

How do you know where the line between economic and “uneconomic” is, based just on this passage? That’s right, you don’t. There’s no support for this conclusion.

(B) damages the environment

Don’t read into it. Just because it “depresses crop yield” doesn’t mean it has anything to do with “the environment” overall.

(C) will eventually make pest problems unmanageable

The passage never mentions “pest problems” or how manageable they are.

(D) …in accordance with manufacturers’ instructions

I told you to read the manual first! Haha. This is bringing in something totally new. It’s also ridiculous and definitely not supported by the passage.

(E) gives financial returns that diminish over time

This all maps. The passage doesn’t mention money, that’s true, but they expect you to know “crop yield” relates directly to “financial returns”. And the “short-term” versus “long-term” stuff in the passage nicely supports “diminish over time”.

(E) is the correct answer.