PrepTest 114

Incorrect. The first line defines endosymbiosis, but it doesn't talk about nucleomorphs, so this answer seems unsupported.

Incorrect. The suspicious word here is all so we should go back to see if the process results in the absorbed organism having all of its genetic material absorbed. Looking at the stimulus, we see that ES is defined as a part of the former becomes a . . . part of the latter so it's not supported that all of it becomes a part of the absorbing organism.

Incorrect. The CA has an unusual nucleomorph, which suggests that there are others that don't share the features of the one here, which is the result of ES. So it's supported that NMs aren't all the result of ES.

Incorrect. The argument never establishes NMs as a necessary condition for ES to happen.

Correct. Argument or Facts:
Facts

Question Type:
Must Be True

Stimulus Summary:
Science.

Just kidding—
ES — One organism absorbs another and they become a hybrid
CA has a weird structure (NM) with two versions of a gene
not NM from an engulfed organism → Single version of gene

Answer Anticipation:
We joked in the Summary but there's a lot of confusing science here. Try not to let it distract you from the logic of the argument! We also used shorthand for all the science words because we didn't want to try to type out chlorarachniophyte . . . ever.

When you run into a Must Be True question like this don't panic! The logic is going to be more important than the content so focus on that. When you see something that is similar to this read through until you find something that presents logic you can work from. Here that last sentence is a conditional—and we know how to work with conditionals. The "if" in the middle of the sentence introduces the sufficient condition so we get (with some shorthand to avoid science terms):
not NM from an engulfed organism → Single version of gene

Alright we can use this! Looking to see how this applies to the situation at hand we can see that the preceding sentence establishes that the NM has two versions of the gene. That's the negation of the necessary condition—the contrapositive therefore lets us then conclude that the NM of the CA is from an engulfed organism. And since the opening line calls the process by which that happens ES we can infer that the CA underwent ES at some point. Now let's translate that back to using the real words so we can look for that answer:
Chlorarachniophytes underwent endosymbiosis at some point in their past which explains their nucleomorphs.

Answer Explanation:
This answer matches our anticipation. The conditional statement in the last line coupled with the fact about the NM of CAs in the preceding line lets us conclude that the chlorarachniophyte formed when it engulfed another organism which is called endosymbiosis. This answer is therefore supported by the logic in the stimulus and is the correct answer.

Key Takeaway:
Don't get lost in the science! The arguments on the LSAT care about logic not content. As such be sure to look for logical relationships and focus on those not scientific ones. And answers that sound too science—y are likely trap answers as they're trying to prey on your fear of the science.