Logical reasoning PrepTest 110 · Section 2 · Question 23

Incorrect. This answer is an illegal reversal of the first conditional.

Incorrect. Being psychologically dangerous is one of the things that it doesn't matter "whether or not" a monster is—it's not sufficient to draw any conclusions. The only thing that can justify a conclusion of not horrific is a monster that is not threatening (the contrapositive of statement #1).

Incorrect. Similar to (B), the only thing that we know guarantees a monster is not horrific is if it's not threatening—so triggering infantile fears doesn't trigger that sufficient condition. In fact, infantile fear is on the list of things that it doesn't matter "whether or not" a monster triggers.

Incorrect. The statement #3 is the only one that presents a sufficient condition for not inspiring revulsion (take the contrapositive)—that condition is that the monster isn't horrific. This answer states that the monster is horrific, so this answer is contradicted by the stimulus.

Correct. Argument or Facts:
Facts

Question Type:
Must Be True

Stimulus Summary:
(1) Horrific → Threatening
(2) Physically dangerous → Threatening
(3) Inspires revulsion → Horrific

Answer Anticipation:
Working through this question is going to very much be about ignoring traps rather than following the logic, so let's talk about why that's the case. Let's talk by talking about the conditional indicator words and how they're diagrammed, then we can talk about all of the extraneous information we left out and how we knew it was extraneous, and then we'll make our anticipation.

So, conditional indicator words. They are, in order: 1) "must"; 2) "if . . . then"; 3) "if." The second two are very straightforward—if/then statements are basic conditionals. "Must" indicates something that is necessary so that's a necessary condition indicator.

Now on to the extraneous information. We left out a lot of the verbiage in the second and third conditionals and the reason for that is that the language suggests that the terms aren't important to the conditional rule. For example the second statement says "[W]hether or not" a monster presents a variety of things the conditional is true. If it doesn't matter "whether or not" those things are true they can't be either sufficient or necessary.

Same with the third statement—"even a" monster with a certain characteristic (being benign) has a rule applied to it. That means that that characteristic can't be sufficient or necessary. To see that think about this parallel example—"All dogs like to play—even chihuahuas." We could throw any breed in and it wouldn't change the meaning at all.

With all that said it's time to anticipate an answer. Statements #1 and #2 share a necessary condition so we can't combine them to form an inference. (If you took the contrapositives and used quantifier rules to determine that not Horrific—some—not Physically dangerous that's a valid inference but exceedingly unlikely to be the correct answer.)

However statements #1 and #3 can be chained together to get:
Inspires revulsion → Threatening
not Threatening → not Inspires revulsion

Answer Explanation:
Just as in the stimulus there's a lot of extraneous information in this answer. However we know three things that guarantee a monster is threatening. Statement #1 tells us that a horrific monster is threatening. Statement #2 tells us that a physically dangerous monster is threatening. And statement #3 when chained with statement #1 tells us that a monster that inspires revulsion is threatening (and this was our anticipated answer). Since this answer discusses monsters that inspire revulsion they're guaranteed to be threatening (#1 + #3) and so this answer is supported. The lack of physical danger and presence of psychological danger are irrelevant to the analysis!

Key Takeaway:
Some Must Be True questions are about knowing what isn't important. Here a lot of factors that were established as not mattering ("whether or not" "even") needed to be ignored to find the answer in an efficient manner.