If a group of words has a noun phrase, a verb phrase, and expresses a complete thought, it is a complete sentence.
Fragment would be ruled out as that is an incomplete sentence that doesn't express a complete thought on it's own. Topic sentences are always complete sentences as well so it is an answer that could fit, however is only used in a certain context like essays or speeches.
The sentence Mandie congratulated win the award for the best class average makes no sense. So, the sentence Mandie congratulated Sophie on the award for the best class average is the best answer.
