Could someone explain the correct answer choice?

Hi Hannah, thanks for the question! The argument boils down to the following: Since we all cherish our close personal relationships, we should not regret missed opportunities from our your, because if acted on, we would not have all of the same close personal relationships we have now. We need to find a principle that would strengthen (most justify) not regretting passing up opportunities in our youth. Answer A says that there are cases in which we should regret; e.g. perhaps in our youth we could have joined a different group of friends that is bigger and remained closer. B simply says if we have a situation in which we now have something we cherish (i.e. our close personal relationships), then we shouldn't regret. Hope this helps!