SAT OwlIn the 1970s, astronomer Vera Rubin found that stars at the outer edges of spiral galaxies orbit just as fast as stars near their centers. Astronomers then had to explain why this ______ the leading explanation is that galaxies contain large amounts of unseen "dark matter."
Which choice completes the text so that it conforms to the conventions of Standard English?
happens?
happens;
happens,
happens
Show answer and explanation
Answer: B
"Astronomers then had to explain why this happens" is a statement that contains an indirect question, so it should not end with a question mark. It is an independent clause, as is "the leading explanation is...," so a semicolon correctly joins them. A comma would create a comma splice.
Choice A treats the clause as a direct question, but "had to explain why this happens" only reports a question and is a statement.
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