SAT OwlFireflies produce light through a chemical reaction that is remarkably ______ very little of the energy it releases is lost as heat, which is why fireflies are sometimes said to give off "cold light."
Which choice completes the text so that it conforms to the conventions of Standard English?
efficient—
efficient,
efficient
efficient, and,
Show answer and explanation
Answer: A
Both sides of the blank are independent clauses, and the second explains what "remarkably efficient" means. A single dash, like a colon, can introduce an explanation after an independent clause. A comma alone creates a comma splice, and no punctuation creates a run-on.
Choice B creates a comma splice, joining two independent clauses with only a comma.
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