Hi there apinkney, thanks for your question! I am assuming that you are referring to the first question, which is the Main Point question, where the correct answer is B. Answer D brings up a concept that is nowhere to be found in the passage, which is that prosperity cannot be measured or defined and that the concept isn't useful. Quite the contrary! The critics here are arguing that we should work to expand our understanding of prosperity by looking beyond strictly monetary measures, and that a greater understanding of that "true" prosperity would be very useful! They aren't saying definition and measurement are impossible, but that the definition should be reconsidered to include other factors. It's not easy, but it's still worth trying, per the last few lines of the passage.
Consider the tone of the passage, which is supportive of a new way of looking at prosperity. Now consider the tone of answer D, which is somewhat dismissive and pessimistic. Not a match at all! There's no way this answer could capture our Main Point when the tone is so far off.
If you were asking about another question in this passage, let us know which one and we'll see what we can do to help. Good luck in your continued studies!
p.s. For more discussion of this passage, including several of the other questions, check out this thread:
lsat/viewforum.php?f=868
Adam M. Tyson
PowerScore LSAT, GRE, ACT and SAT Instructor
Follow me on Twitter at
https://twitter.com/LSATadam