Final answer:
The correct punctuation for the sentence 'Are you sure you haven't seen my homework' is a question mark (?) because the sentence is a question. The correct answer is option a. ?.
Step-by-step explanation:
The sentence in question is "Are you sure you haven't seen my homework" which should end with a question mark because it is phrased as a question. Therefore, the correct punctuation to use at the end of this sentence is option a. ? A period is used to end declarative (statement) and imperative (command) sentences, and an exclamation point is used for sentences that express strong emotion or surprise.