LSAT Explanation PT 20, S1, Q4: An ingredient in marijuana known as
LSAT Question Stem
Which one of the following, if true, most seriously weakens the argument?
Logical Reasoning Question Type
This is a Weaken question.
Correct Answer
The correct answer to this question is B.
LSAT Question Complete Explanation
The question type for this problem is Weaken, which means we are looking for an answer choice that undermines the conclusion or the relationship between the premises and the conclusion.
Let's break down the argument in the passage:
Premise: THC in marijuana inactivates herpesviruses.
Premise: Inactivated herpesviruses can convert healthy cells into cancer cells.
Conclusion: Marijuana can cause cancer.
Our goal is to find an answer choice that weakens this conclusion. Before we discuss the answer choices, let's think of an "Evaluate" question for this argument: "Are there any other factors or ingredients in marijuana that could affect the relationship between THC and cancer cells?"
Now let's analyze the answer choices:
a) Several teams of scientists performed the various experiments and all of the teams had similar results.
- This answer choice does not weaken the argument. If anything, it strengthens the conclusion by providing more credibility to the results. Therefore, this is not the correct answer.
b) The carcinogenic effect of THC could be neutralized by the other ingredients found in marijuana.
- This is the correct answer choice. If there are other ingredients in marijuana that neutralize the harmful effects of THC, it weakens the conclusion that marijuana causes cancer.
c) When THC kills herpesviruses it weakens the immune system, and it might thus diminish the body's ability to fight other viruses, including viruses linked to cancers.
- This answer choice actually strengthens the assertion that marijuana use increases the risk of cancer, so it is not the correct answer.
d) If chemists modify the structure of THC, THC can be safely incorporated into medications to prevent herpes.
- The effects of a modified THC have no bearing on assessing whether marijuana increases cancer risk. This answer choice is not relevant to the argument, so it is incorrect.
e) To lessen the undesirable side effects of chemotherapy, the use of marijuana has been recommended for cancer patients who are free of the herpesvirus.
- The fact that marijuana has been recommended for cancer patients does not make it more or less likely that marijuana use causes cancer. This answer choice is irrelevant to the argument, so it is incorrect.
In conclusion, the correct answer choice is (b), as it weakens the argument by introducing the possibility of other ingredients in marijuana neutralizing the carcinogenic effect of THC.