LSAT 91 - Section 2 - Question 06

This is an RRE question.

The stimulus tells us that according to a new study, after a heavy rainfall, pollution levels in Crystal Bay reach their highest levels. We also learn that rainwater is almost totally pure. Together these constitute the phenomenon we are trying to explain. The stimulus also tries to generate a feeling of surprise or puzzlement by telling us what we should expect. That is, we should expect the pure rainwater to dilute the polluted seawater.

As with all RRE questions, whether or not we feel like the phenomenon is puzzling largely depends on what assumptions we were making. If we assume that the stimulus paints the whole picture, in other words, the phenomenon is merely as simple as that which the stimulus describes, then we might think this is surprising. On the other hand, if you are a subject matter expert, say someone who studies urban pollution, you probably already know that there are other factors at play. You probably already know the explanation for the phenomenon.

We don't need to be subject matter experts to get RRE questions right. We just need to keep an open mind about possible explanations.

Correct Answer Choice (B) says most of the rainwater that eventually reaches Crystal Bay falls on pesticide-treated fields before being carried into the bay. This is a specific version of what I described generally above. The story is indeed more complicated. While it's true that some rain falls directly into the bay and would have the effect of diluting the pollution in the bay, as it turns out, most rain doesn't fall directly into the bay. Rather, it falls onto land and then runs off into the bay, picking up and carrying whatever it is that it comes into contact with. This answer choice specifically tells us that it picks up and carries pesticides into the bay. We only need to assume that pesticides are a type of pollution.

Answer Choice (A) says compared to the total amount of polluted seawater in Crystal Bay, the amount of rainwater that falls into it is negligible. This answer choice might have worked had the phenomenon been different. If the phenomenon merely said that after a heavy rainfall, pollution levels remain unchanged in Crystal Bay, then perhaps this answer provides an explanation. Yes, it's true that rainwater is pure, which would dilute polluted seawater. But in order for the dilution to be measurable, there needs to be some minimum threshold amount of rainwater. For example, if you simply pour a bucket of rainwater into the bay, nobody would expect the pollution to be diluted because a bucket of rainwater is a negligible amount. That's what this answer choice provides. The explanation is that there just simply isn't enough rainwater. Fair enough, but the phenomenon above that we are trying to explain isn't that pollution remains unchanged after rainfall. Rather, it's that pollution reaches its highest levels after heavy rainfall. This answer does not explain that at all.

Answer Choice (C) says most rainwater carried by clouds consists of water that's evaporated from oceans around the world. This is irrelevant. C tells us the origins of rainwater. It treats rainwater as an effect and reveals to us rainwater's causes. We simply don't care about that. We already know rainwater is pure, and that sets up the expectation of diluting pollution in Crystal Bay. We’re simply trying to explain why that expectation was upset.

Answer Choice (D) says the single leading cause of pollution in Crystal Bay is beachgoers leaving behind trash which blows into the bay. In order for this answer to explain the phenomenon, we have to assume that heavy rainfall somehow causes more trash either to be left behind or to be blown into the bay. We might be tempted to say that rainfall tends to be accompanied by strong winds which would blow more trash and debris into the bay. Fair enough, but it still remains to be explained why the rainfall itself, which is mostly pure water, doesn't counteract the extra pollution from the trash by diluting the existing pollution in the bay. Contrast this answer with Answer Choice (B). There, we have no such lingering question. We are told there that most rainwater that reaches the bay carries pollution, which means that it's only a minority of rainwater that reaches the bay in its pure form.

Answer Choice (E) says other nearby ocean areas experience a pattern of pollutant increase and decrease that is extremely similar to that of Crystal Bay. This is a cookie-cutter wrong answer for RRE questions. This answer reveals a phenomenon consistent with the phenomenon in the stimulus and is also in need of an explanation just like the phenomenon in the stimulus. So rather than solving the problem, this answer only adds to the problem.