Quincy responds to Pamela, who claims that medical residents' long shifts are problematic because the resulting fatigue causes them to make worse decisions. In responding, Quincy says that residents have been shown to make reasonably good decisions when this shift structure has been used in the past. Quincy's unstated conclusion is that there's no need to change the length of residents' shifts. Even if they would theoretically make better decisions, their current decision-making is good enough, as it has been in the past.

Quincy's argument rests on an analogy to the past: because long shifts worked fine in the past, we should expect them to keep working fine. So to counter (i.e. weaken) Quincy's argument, we can attack the analogy by showing that there's some relevant difference between the past and now. We want an answer to establish that something has changed over time, creating a need for better decision-making from medical residents.

Keep in mind though, it's always possible that we might not find our predicted answer. In this case, we'll want to read carefully and rely on a process of elimination to narrow down our options. Ultimately, the correct answer needs to show why Quincy is wrong, and long shifts which cause fatigue are not good enough.