16Hit1600
Standard English ConventionsMediumNonessential appositive set off by commas

Standard English Conventions practice question

The observatory's oldest ____ a brass refractor built in 1861, is still used on open nights.

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

  1. A. instrument,Correct
  2. B. instrument
  3. C. instrument;
  4. D. instrument—

Answer: A. instrument,

'A brass refractor built in 1861' is a nonessential appositive; the comma after it is given, so a matching comma must open it.

Why the other answers are wrong

B. instrument
Without an opening comma, the appositive has a closing comma but no opening one.
C. instrument;
A semicolon can't open an appositive.
D. instrument—
A dash would need a matching dash, not the comma that follows.

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