GMAT Club World Cup 2022 (DAY 1): One perplexing result of General

Manhattan Prep Official Explanation:

First Glance: Differences in the answer choices provide clues about what a problem might be testing. Before reading the sentence, glance at the beginning of the underline and down the beginning (just the beginning!) of the five answer choices to look for one early clue as to what this sentence is testing. In this case, the entire sentence is underlined, so there’s a good chance that at least one of Sentence Structure, Meaning, Modifiers, and/or Parallelism will be tested. Keep an eye out for these things as you read the original sentence.

Issues:

(1) Parallelism
In the original sentence, the word and requires parallelism. There is another that construction earlier in the sentence:

One perplexing result is the prediction…

(X) that gravitational singularities lie at the hearts of black holes
(Y) that has been supported by subsequent research

There are two errors. First, gravitational singularities lie is a complete subject-verb pairing, while has been supported is just a verb structure that takes prediction as its subject. These two elements are not structurally parallel. Second, if a prediction has been supported by subsequent research, then it is illogical to say that the prediction is perplexing for that reason. Rather, just the X element is perplexing for some reason. (Note: You don’t need to know about General Relativity or understand why! Just trust the sentence when it says that this observation is perplexing to scientists.) Eliminate choice (A).

Choices (B) and (E) have similar parallel constructions at the end. Examine choice (B) first. One possible way to read it is as follows:

One perplexing result is…

(X) the prediction at the heart of each black hole of a gravitational singularity
(Y) a prediction that has been supported by subsequent research

In this reading, from a purely technical parallelism standpoint, the prediction and a prediction are parallel because they’re both nouns with modifiers afterwards, although it’s awkward to make the exact same prediction parallel to itself. (Is there just one prediction? Are there two?) In addition, the illogical meaning is repeated: A prediction that has been supported by subsequent research is not perplexing for that reason. Eliminate choice (B).

There isn’t anything elsewhere in the sentence that could be made parallel to but a prediction, so there’s no correct X element match for this part of the sentence.

Here is choice (E)’s parallel structure:

The prediction that [something is true] is…

(X) a perplexing result
(Y) supported by subsequent research

The meaning is logical—only the result is described as perplexing—but the two elements are not in the same structural form. Element X is a noun (result) while element Y is part of the verb form is supported.

(2) Modifier / Meaning

While examining the X element in choice (B), you might also spot that something is going on with the modifier: the prediction at the heart of each black hole of a gravitational singularity. In the moment, you can decide whether to continue examining the parallelism or to examine the modifier instead; choose whichever path you think is easier/faster for you.

The order of modifiers in choice (B) creates an illogical meaning. It appears to imply that the prediction itself is located at the heart of each black hole or perhaps was made at the heart of the black hole? The prediction is not, of course, at the heart of a black hole, so eliminate (B) for faulty meaning.

(3) Meaning

Choices (C) and (D) change the sentence structure (there is no longer parallelism at the end), so examine the core sentence structure of each. The core subject-verb pairing in choice (C) is logical and structurally sound: One of the perplexing results … is the prediction … [that something is true]. In choice (D), however, the core subject-verb pairing is problematic:

The prediction [of a certain thing] is a point where [something else happens].

The prediction itself is not the point where some particular thing happens. Rather, that phenomenon occurs within a black hole. Eliminate choice (D) for illogical meaning.

The Correct Answer: Choice (C) correctly labels only the gravitational singularity phenomenon as perplexing. Further, this choice employs modifiers, rather than a parallel structure, for the two extra pieces of information it is providing. The first modifier, supported by subsequent research, is correctly placed immediately after the noun that it is modifying, the prediction. The second modifier, a point at which … apply, is correctly placed immediately after the noun that it is modifying, a gravitational singularity.

Note: The split in the answer choices between where and at which is a red herring. Both constructions are correct. In addition, the variations one perplexing result and one of the perplexing results are also both correct.