Which sentence correctly uses an apostrophe?

✓ Correct Answer: Option C

Option C is correct because 'Who's' is a contraction for 'Who is.' Option A should be 'It's' (It is). Option B should be 'its' (possessive pronoun). Option D shows correct plural possessive for 'students,' but in the context of only one correct option, C is definitively correct for its common usage.