Logical reasoning PrepTest 131 · Section 1 · Question 12

Incorrect. In concluding that the rise in cancer rates is not due to synthetic carcinogens, the author is implying something else is the cause. Nonsynthetic pollutants could serve as this alternative cause, so the author doesn't overlook this possibility—this possibility helps her argument.

Incorrect. Similar to (A), in bringing up an alternative cause of the increased cancer rates, this answer strengthens the argument that it's not synthetic carcinogens, and thus it doesn't highlight a possibility the author overlooks.

Incorrect. The argument centers around what isn't the cause of the recent increase in cancer rates, so other illnesses caused by these compounds are out of scope and thus it's not a flaw for the author to overlook them.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Errors in Reasoning

Stimulus Summary:
Phenomenon - Increased cancer rate
Potential explanation 1 - Synthetic carcinogens used in food production
Potential explanation 2 - Nonsynthetic carcinogens found in plants/animals
There are significantly more nonsynthetic carcinogens than synthetic ones, so explanation 1 is absurd.

Answer Anticipation:
This argument presents a phenomenon and a couple potential explanations for it. It then rules out one explanation, though it doesn't go so far as to side with the other explanation. So we need to explain why the argument is flawed in ruling out the one explanation.

So what's the basis for doing so? Well, there are more nonsynthetic carcinogens than synthetic ones, so the author believes the latter can't be the cause of the cancer rate increase.

Does the number of a class of carcinogen determine its impact on the cancer rate? Maybe, but it's not definitive. There are other factors at play—how much are people exposed to those substances, how carcinogenic are they, etc . . . Answers that bring up other considerations as to how a class of compound could affect cancer rates other than the number of such compounds will highlight the error in reasoning here.

Answer Explanation:
The argument uses the relative number of synthetic and nonsynthetic carcinogens to support the conclusion that the category that has fewer members—the synthetic carcinogens—can't be driving an increase in cancer rates. This answer raises the possibility that it's not the total number of compounds in a category that determines its impact on cancer rates, but rather people's exposure to those compounds. If people are more frequently exposed to the synthetic carcinogens, they could drive the increased cancer rate even if there are fewer of them. This answer highlights a possibility the argument overlooks.

Key Takeaway:
When the LSAT uses one metric to draw a conclusion without establishing it's the relevant metric, the correct answer will frequently feature another metric. Here, the argument used the number of a certain substance to downplay its effect, and the correct answer highlighted exposure to the substances as an alternative metric to measure/predict it.

Incorrect. This answer seems to bring up a separate consideration other than the number of compounds—how carcinogenic the substances are. However, there are two issues. First, this answer doesn't discuss whether this is true of synthetic carcinogens, so we can't tell if this would impact which of the two is more likely the cause of the increased cancer rates. Second, this answer doesn't provide enough information to analyze—does the susceptibility vary from "very susceptible" to "unbelievably susceptible," from "not susceptible at all" to "very susceptible"? Without knowing the range, it's hard to know how this plays into the overall cancer rate.