Which sentence uses "their," "there," or "they're" correctly?

Which of the following sentences is grammatically INCORRECT?

Identify the sentence written in active voice.

Which sentence has the right spelling?

In grade school you were disciplined by the _____.

What is the name for two words with opposite meanings?

Which uses the homophone correctly?

What is the distinction in usage between "toward" and "towards"?

Traditionally, how does a proofreader indicate that words or instructions written on a proof SHOULD NOT literally be set into type?

What does the Latin abbreviation "ibid.", found in bibliographies, mean?

What is the traditional proofreading mark for adding italics?