Official Explanation

Identify the Question Type:

The blank at the end of the stimulus and the phrase “best completes the passage” indicate this is an Inference question. The correct answer will logically follow from the stimulus without requiring any additional information.

Untangle the Stimulus:

The stimulus describes the negative effects of chlorofluorocarbons. It concludes by saying that chlorofluorocarbons should not be used, "especially since ____."
Predict the Answer:

The correct answer will provide a logical reason to discontinue the use of chlorofluorocarbons that is line with what the stimulus states. Note that the stimulus already set forth the negative effects of chlorofluorocarbons. It would have been enough to conclude that chlorofluorocarbons should not be used. The word "since" before the blank indicates the author's looking to provide yet one more piece of evidence to avoid their use. Although it's impossible to know what that evidence will be for sure, it will provide another, new reason to not use chlorofluorocarbons.

Evaluate the Choices:

(D) is the correct answer, because it gives an additional reason to stop using chlorofluorocarbons - one that deals with the possible objection of what would we do instead?

(A) doesn't follow from the rest of the stimulus. Perhaps if most people live in areas where the protective ozone layer is thinnest, there would be extra urgency is stopping the use of chlorofluorocarbons. But (A) says the opposite.

(B) doesn't follow logically from the stimulus. Whether users of chlorofluorocarbons are aware or unaware of the risks involved is irrelevant. The stimulus already gave the reasons to stop using chlorofluorocarbons. (B) doesn’t add to those reasons, and certainly doesn't deserve to come after the emphasis word, “especially.”

(C) does not state another reason to stop the use of chlorofluorocarbons. The stimulus already said that “even the smallest amounts of chlorofluorocarbons” do damage. The answer shouldn't create a redundancy in the argument.

(E) reinforces the importance of ozone, but does not add anything new enough to merit appearing after the emphasis word, "especially." The stimulus already discussed some benefits to human life. The stimulus already said chlorofluorocarbons should not be used. The use of the words, "especially since" give the impression that something new and uniquely important is coming up. (E) is not the type of thing expected.

Answer: D

TAKEAWAY: With complete the passage Inference questions, the answer will always something that completes the train of thought.