Prolonged exposure to sulfur fumes permanently damages one's sense of smell. In one important study, 100 workers from...

Naz on November 3, 2014

We are looking for the answer choice that either strengthens or does nothing to the argument. So four answer choices will weaken the argument, while one--the correct answer--will either strengthen or do nothing.

Answer choice (D) states: "Every sulfur-emitting factory with workers participating in the study also emits other noxious fumes."

If all of these sulfur-emitting factories also emit other noxious fumes, then it doesn't necessarily have to be the prolonged exposure to sulfur that is causing permanent damage to one's sense of smell, it could be the other noxious fumes.

Thus, answer choice (D) weakens the argument because it no longer necessarily has to be the sulfur fumes that are causing the damage to one's sense of smell--it could be any one of the other noxious fumes present in all those factories.

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