Logical reasoning PrepTest 111 · Section 4 · Question 22

Correct. Argument or Facts:
Facts

Question Type:
Cannot be True

Stimulus Summary:
MS: White blood cells attack myelin sheaths. It can be treated with a drug.

Old theory - MS was caused by viruses
Test - Give people with MS gamma interferon, which is one way the body fights viruses
Result - Those patients given GI ended up with bad MS flare-ups

Answer Anticipation:
First, let's discuss the question type. Four of the answers will be compatible with the information in the stimulus, whereas one won't be. Being compatible with information isn't the same as needing to be true based on it, so we shouldn't view this as a Bizarro Must be True question. However, being incompatible with information does mean that something Cannot be True, so let's approach it as that question type (though since it does state LEAST compatible, we shouldn't rule an answer out because it's really unaligned with the information but still technically possible).

With that noted, the key here is to not let ourselves get mixed up in the science here. When we're trying to avoid getting bogged down in complex content, we should focus on logic. And science is almost entirely about causality.

Here, we get a few causal relationships:
(1) White blood cells attacking myelin sheaths causes MS
(2) Gamma interferon fights viruses
(3) Gamma interferon makes MS worse

The correct answer will most likely be incompatible with one of these three relationships, while the others make sense in the context of them, so let's analyze the answers using that framework.

Answer Explanation:
It's noted that MS is a disease where white blood cells attack the myelin sheath, and that gamma interferon made MS worse. As such, it doesn't make sense for gamma interferon to stop the white blood cells from attacking the myelin sheath, as that would make MS better! This is the correct answer.

Key Takeaway:
Science is mostly focused on explaining causal relationships. When you're in a science passage that has complex content, focus on these causal relationships, as they'll lead you to the correct answer most of the time.

Incorrect. White blood cells are at the root of MS. If gamma interferon causes those without MS to produce more white blood cells, that suggests that it has the same effect on those with MS. As such, it makes sense that giving it to the MS patients would make them worse since it's resulting in more of the cause of MS to be present.

Incorrect. While correlation doesn't equal causation, it does support it. If gamma interferon levels are correlated with MS, then it makes sense that giving it to MS patients would make the MS worse.

Incorrect. Gamma interferon is an antiviral weapon. If MS was caused by viruses, then it would make sense that gamma interferon would make MS better. So it makes sense, since gamma interferon made things worse, that MS isn't caused by viruses.

Incorrect. If a drug that successfully treats MS inhibits the activity of gamma interferon, then that suggests it's possible GI is related to MS. As such, it makes sense that the patients who were given GI ended up with their MS getting much worse.