The answer to your question would be that the sentence that uses the word "synthesize" correctly is the following one: The final exam asked the students to synthesize what they had learned all year. That is, your answer would be D.
The Cambridge dictionary defines "synthesize" as "to put separete facts, etc. together to form a single piece of work". In this case, the "separate facts" would be the bibliography you used and the assignments you took during the course.
