anyway, still feel A is weird becasue the arg already saying "even if volunteering does not boost longevity", does n't it mean that no matter how you find any evidence about any group, as long as the evidences are about volunteer, it is already excluded by the arg. In this case, I vote for C.
个人认为lawyer是对的,关键在于对问题的理解:However, that statistic would be what we should expect even if ... 换句话说:that static would be true even if volunteering does not boost longevity