PrepTest 124

Correct. Argument or Facts:
Facts

Question Type:
Must Be True

Stimulus Summary:
A book will contain essays by L, K, or J, but not all three.
K → J

Answer Anticipation:
This question almost feels like a logic game!

The first statement is background, but then we get to the real stimulus, which presents us with two pieces of information. The first statement is essentially an "at least one, but not both" statement, although it includes 3 variables, so it's more of an, "at least one, but not all three"—or one is in, one is out, and another could be either in or out.

The second is a conditional that relates two of the authors. Let's take the contrapositive of it so we can work with both:
K → J
not J → not K

If K is in, then so is J, and therefore L must be out in order to satisfy the condition that not all three authors have an essay in the book. On the other hand, if J is out, then so is K, and therefore L must have an essay in the book so that at least one of J, K, and L has an essay in the book

So we can infer that K → not L, and L → not K based on the "group" sizes here—just like in an LG!

Answer Explanation:
This answer is supported by the information. Either L, J, or K is going to be left out of the book. If L is in, there's only room for one of the other two, and K brings J along with her, so K can't be included.

Key Takeaway:
If something in one section is triggering your spidey-sense for another section, listen to it! There is overlap between the sections, and Must Be True questions show up in LG more frequently than they do in LR.

Incorrect. The book can contain essays by just K and J, or just L and J.

Incorrect. The book can contain an essay by K as long as it also contains an essay by J and no essay by L.

Incorrect. If the book contains an essay by L, there's no reason that an essay by either other author needs to be included.

Incorrect. The textbook could contain an essay by K and J, or just J—there's no need for an essay by L to be included.