This question is good for helping you exercise your "find the alternative explanation" muscle.
THE FACTS (MUST BE TRUE)
-Established causal relationship: helping others ---> endorphins--->feeling of well being
-Established correlational relationship: volunteers live longer, on average, than non-volunteers
THE HYPOTHESIS (MIGHT BE TRUE OR MIGHT BE FALSE)
-Proposed causal relationship: endorphins---> long life
*IF* this proposed relationship were true, then volunteering (a form of helping others) -->endorphins--->long life
BUT the conclusion, signaled by the word "However," is that the Established correlational relationship (volunteers live longer) would be true even in the absence of the proposed cause for it (endorphins). Your job is to figure out why.
In simpler terms: we know volunteering (a form of helping others) will cause endorphins. But what might account for the fact that volunteers live longer *other than* the proposed causal relationship?
Note: There's a sneaky jump in wording here--notice the conclusion says "even if VOLUNTEERING does not boost longevity" rather than "even if ENDORPHINS do not boost longevity." This actually makes your job a little easier because you are examining an even more specific chain of causation: *volunteering-->endorphins-->longevity? * rather than the broader endorphins--> longevity.
Choice (A) neatly cuts out the necessity for any causal link between endorphins and longevity by explaining that the longer-than-average lifespans of volunteers is due to the fact that these volunteers are women. Volunteers are likely to be women who are likely to live longer; therefore the volunteers are likely to live longer. YES!
Choice (B) is incorrect because the number of volunteers in the population is irrelevant to the phenomenon we are trying to explain (volunteers living longer). Also, we are looking for an explanation for longevity that is not related to people's volunteering activities!
Choice (C) is also incorrect because it doesn't explain longevity. Endorphins may mask symptoms --for a time-- but that doesn't mean those people live longer.
Choices D and E are incorrect for reasons similar to the reason choice B is incorrect. We're looking for a cause of longevity *other than* volunteering and the endorphins it creates. Out of scope.
Hope this helps.
JP Park | Manhattan GMAT Instructor | Los Angeles
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