(A) does the opposite of what we want: it strengthens the similarity between the past and now that Quincy is relying on. If responsibilities haven't changed, then why should the length of shifts?

(B) tells us that something has changed since the past: hospital patients are sicker than they used to be. We can make a reasonable assumption that it's harder to care for sicker patients, so we probably want residents to be more on top of their game.

(B) isn't a perfect answer, but in the context of the other answer choices, it's still the best we have. No other answer choice gives a reason why we would want residents to be making better decisions than has been acceptable in the past.

(C) offers support for long shifts, although maybe not quite 36 hours. But by giving an affirmative reason that residents should work long hours—to provide continuous care—(C) just adds another reason not to change anything.

(D) tells us that residents' workload can vary, but it doesn't say enough to convince us that avoiding fatigue is more important than it used to be. Even with these variable workloads, residents' decision-making was still good enough in the past. This doesn't address Quincy's question—why change things now?

Like (C), (E) gives an affirmative reason for long shifts: residents should observe patients over an extended period of time. This does the opposite of weakening Quincy's argument. It shows us there's a good reason for long shifts, so maybe the fatigue is worth it.