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Difficulty: Very hardParallel Structure

Theoretical models of planetary formation often emphasize the initial abundance of heavy elements in a protoplanetary disk. However, in analyzing the accretion rates of Jovian planets, astrophysicist Elena Vance argues that a nascent world's ultimate size depends not on how rapidly it accumulates local gas and dust from the disk during its early formation phase, but on ______

Which choice completes the passage so that it conforms to the conventions of Standard English?

  1. how efficiently it clears nearby planetesimals from its orbital pathway.Answer
  2. B
    clearing nearby planetesimals from its orbital pathway efficiently.
  3. C
    the efficiency with which nearby planetesimals are cleared from its orbital pathway.
  4. D
    whether it can efficiently clear nearby planetesimals from its orbital pathway.

Answer

The correct answer is the clause that mirrors the structure of the first element by starting with the conjunction 'how' followed by an adverb, subject pronoun, and active verb: 'how efficiently it clears nearby planetesimals from its orbital pathway.'
The correct option is correct because it uses a dependent clause that perfectly mirrors the grammatical structure of the first clause in the comparison. The first clause, 'how rapidly it accumulates...', is structured as a subordinating conjunction ('how') followed by an adverb ('rapidly'), a subject ('it'), and an active verb ('accumulates'). The correct option follows this exact pattern: 'how' + adverb ('efficiently') + subject ('it') + active verb ('clears'). This maintains a balanced and parallel sentence structure.

Step-by-Step Solution

1
Identify the comparative structure in the sentence.
The sentence uses the correlative comparison 'depends not on [X], but on [Y]'.
Parallel structure requires that X and Y have matching grammatical forms after the preposition 'on'.
2
Analyze the grammatical structure of the first element (X).
The first element is 'how rapidly it accumulates local gas and dust...', which is a noun clause structured as: conjunction ('how') + adverb ('rapidly') + subject ('it') + active verb ('accumulates') + object ('local gas and dust') + modifiers.
To maintain parallelism, the second element (Y) must follow this exact same grammatical pattern.
3
Evaluate the choices to find the one that matches this pattern.
The option containing 'how efficiently it clears nearby planetesimals from its orbital pathway' uses the exact same pattern: conjunction ('how') + adverb ('efficiently') + subject ('it') + active verb ('clears') + object ('nearby planetesimals') + modifiers.
Matching grammatical structure ensures the sentence is parallel and grammatically correct.

Key Concept

Parallel Structure
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Topics

Parallel Structure

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