Answer:
(A) in the communities studied, women were much more likely to do regular volunteer work than men were, and women tend to live longer than men do.
Explanation:
In the text three associations are made:
- volunteering --> endorphin release
- endorphin release ---> longevity
- volunteering ---> longevity
The question is why it might be the case that those who volunteer might, on average, live longer, than those who don't, even if the volunteering itself isn't conferring any benefit. In any other words, there must be something about the volunteering population that accounts for them having a longer life expectancy. We're looking for that something else - what feature does this group have that accounts for their longer lifespans?
Answer A is the only one that is relevant, stating that if women are disproportionately represented among volunteers, and women live longer than men do, then we'd expect volunteering populations to live longer than non-volunteering populations, even if volunteering wasn't conducive to long life.