Hi Maria,
Great question. When answering main point questions, one great tip is to do them last, after working through the rest of the questions for that passage. You will likely have a much better grasp of the main point after working with the passage for 8-9 minutes. Alternatively, answer the MP first, but then doublecheck your answer before moving on to another passage.
Also, remeber that when all the answers seem equally bad, go for the answer that 1) you can prove: these are still Prove-family questions, and 2) that covers the most textual "real estate" on the page. Correct MP answers rarely focus on a single paragraph of the passage.
So with this specific passage, the first paragraph discuusing the comic book style combined with the long last paragraph discussing Roy's realism and nostalgia help push us towards Answer choice (B).
But if you apply our real estate advice between (A) and (B) you will also see that Answer Choice (A) is really limited mostly to the short first paragraph while Answer Choice (B) has a lot more text!
Thanks and I hope that helped.