Sure thing. If you want a "cheat code" for PURPOSE OF A PARAGRAPH questions, the correct answer is normally some form of paraphrasing the topic sentence of the paragraph (maybe the first two sentences).
Here the topic sentence of P2 is that "theoretical equipoise may be too strict".
To CONFIRM that this is the big idea dominating the 2nd paragraph, I want to see that the author goes on to unpack / support the claim that "theoretical equipoise may be too strict".
And indeed, we see the author build that argument in 17-32, culminating with his conclusion "Consequently" -- the overly strict standard of theoretical equipoise would result in bad constraints on research.
(A) The AUTHOR is in favor of clinical equipoise. In this paragraph he's not outlining the position of people who favor theoretical. He's showing us why HE doesn't like theoretical.
(B) This sounds neutral and not-author. We were looking for something that sounded like "theoretical equipoise may be too strict".
(C) Maybe ... negative towards theoretical equipoise ... but MORAL principle? That doesn't sound familiar.
(D) Boom. Negative towards theoretical equipoise. Better than (C) because there's nothing funky sticking out here. What IS the main difficulty? It's that "consequently" payoff line at the end of the 2nd P.
(E) GENERAL notion of equipoise? This paragraph is specifically about THEORETICAL equipoise.
(D) is the correct answer.Cheat code wins this time.