For RC, the questions I struggle the most with are tone questions and author's perspective, specifically questions where I'm asked to infer about what the author would agree with/presume. Like many others, I was in between B and C for this question.
One of the explanations is that the passage is only concerned with reporting other people's opinions, and not the other's own. But I have trouble squaring this explanation for AC B with the explanation for Q22 which is asking for author's tone. If the correct answer in Q22 is that the author is sympathetic with Carroll and Chen's theory, then why can't we argue that for this question, the author would agree with AC B?
Regarding C -- Last time I took physics was in HS and I've completely forgotten it! So, precisely because I don't know physics, to me this statement ("A hot and dense state is a state of low entropy") seemed very broad? The passage only said that the small, hot dense state that was the initial condition of our universe was a state of low entropy. And I thought this was different than a more broad general physics law-like sounding rule (Hot + Dense = Low entropy).
I'm taking the LSAT in a couple of days, and these Author's perspective questions still get me!