"Unstated Assumption"

What do you mean by "identify"? If it is unstated, how can you identify it?

@hales and @Kristin-Swope-2, Happy to help. @hales, in general, it's important to scrutinize the stimulus and always be thinking if they're making an assumption with their argument. On this question, we're actually told what the unstated assumption is ("some patients who take penicillin develop bacteria with an immunity to penicillin"), so they did the work for us. @Kristin-Swope-2, by "identify," we mean that we need to figure out the role that the unstated assumption plays in the argument. You're right, the assumption is unstated, but it's actually given to us in the question stem. This is a causal argument. The effect is that people who don't take penicillin still develop penicillin-resistant bacteria. The scientists have concluded that the cause is mercury dental fillings. The way it works it that penicillin-resistance is closely related to mercury-resistance, so the non-penicillin resistant bacteria are dying off even though there is no penicillin. The question stem explicitly gives us an unstated assumption and asks us about what role it plays. Some patients who take penicillin develop penicillin-resistant bacteria - what role does that play? It doesn't really provide support for other statements in the stimulus, so we're anticipating that it's just going to be some background information necessary to understand the argument. (C) says, "It is a point that, in conjunction with the fact that some patients who do not take penicillin develop penicillin-resistant bacteria, generates the problem that prompted the research described in the passage." (C) looks great. The idea that some people who don't take penicillin have penicillin-resistant bacteria isn't a mystery unless the common conception is that taking penicillin is what causes the resistance, so (C) is the correct answer choice. Does this make sense? Let us know if you have any other questions!