Will someone please explain this question to me?

Thanks

Sure.

The conclusion is that $ doesn't guarantee happiness. Why? Because in a survey, only 1/3 of those who say they were financially successfully claimed to be happy.

So, what's the gap in this argument we need to strengthen?

One issue is that the conclusion is based on those people that said they were financially successful. Were they really? What if of the, say, 90 supposedly rich (financially successful) people surveyed (and we don't know how many people were polled in total), only 30 of them were actually rich? And it turns out they were the 1/3 that said they're happy.

(A) helps fill this gap by saying those folks were actually rich.

(B) is about what is thought and was thought. It doesn't address the premise-conclusion link. Out of scope.

(C) is about people that did NOT claim to be rich. We don't care about them right now.

(D) has the same issue as (C).

(E) is tempting. What if the 2/3 of people that said they're unhappy weren't actually unhappy? What if they were actually happy?!
The issue is that we don't know the extent of the poll. Let's imagine that while 90 people said they're rich, 800 people were surveyed. That means that 710 people did not claim to be rich. If half of them said they're unhappy, and they, as (E) suggests, were lying, it doesn't affect the argument. We care about whether the supposedly rich people's answers to the poll means what the conclusion says it does about them.

That help?

Thank you Noah. I understand it better. I appreciate your help.