Logical reasoning PrepTest 138 · Section 2 · Question 10

Incorrect. The stimulus discusses individual cats, not breeds, so this answer is out of scope.

Incorrect. It's unclear what a "type of allergy sufferer" is, so this answer is also out of scope.

Correct. Argument or Facts:
Facts

Question Type:
Must Be True

Stimulus Summary:
Cat allergies are caused by skin and saliva proteins
Different people are allergic to different proteins
All cats cause allergies in some
Cats commonly cause allergies in only some and not others

Answer Anticipation:
There are a lot of individual statements here. There are comparisons, conditionals, causal statements—it's a mish-mash of the Must Be True greatest hits!

All of these statements deal with the same concepts, but there's not a clear inference—no chains, for example. So we'll have to get an understanding of what's going on and see what inferences or generalizations we can draw.

We do know that cats all cause allergies in some people, but they also don't cause allergies in all people with cat allergies. In other words, a person is allergic to some cats, but not others. What can explain that? The proteins in the skin and saliva are the allergens, so to cause allergic reactions in some but not others, cats must have different protein allergens from each other. Let's find an answer bringing up that comparison.

Answer Explanation:
Since it's "common" for cats to cause allergic reactions in some cat allergy sufferers but not others, those other allergy sufferers must be allergic to other cats (otherwise they wouldn't be "people who are allergic to cats."). Since we've got different cats triggering allergies in different people and it's the proteins in skin/saliva that cause those allergies, cats must not all have the same allergy-inducing proteins. This answer is supported by the stimulus.

Key Takeaway:
Some Must Be True questions don't have a rote means by which you can draw an inference (e.g., chaining together conditionals). For these, you'll have to understand the statements and how they overlap.

Incorrect. There's no discussion of allergic reaction intensity, so this answer is out of scope.

Incorrect. There's no discussion of predicting whether a given cat will cause allergies—maybe those proteins can be tested. This answer is also rather extreme in stating that there is "no way" to determine something—that's stronger than the statements in the stimulus.