SAT OwlThe idea that the Moon's gravitational pull, acting on Earth's oceans over billions of years, has gradually slowed Earth's ______ is supported by fossil corals whose growth rings record more days per year than there are today.
Which choice completes the text so that it conforms to the conventions of Standard English?
rotation,
rotation;
rotation
rotation—
Show answer and explanation
Answer: C
The long subject of this sentence is "The idea that ... has gradually slowed Earth's rotation," and the main verb is "is supported." No punctuation should separate a subject from its verb, no matter how long the subject is. The commas around "acting on Earth's oceans over billions of years" are already paired, so nothing more is needed.
Choice A is tempting because the subject is so long, but a comma here would separate the subject from its verb "is supported."
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