Answer:
B. Successful students study often, work hard, and turn in assignments on time.
Explanation:
If you look at the presented answers, you notice that with answer A, the sentence structure is not correct when it says, "Study often, work hard, and turning in assignments. Turning in assignments is not appropriate with the presented sentence structure. With choice C, it shows "successful students study often, working hard to turn assignments in on time. That could work as a sentence, but it eliminates the fact that the students work hard in class too, not just to turn certain assignments in. Choice 4 also presents improper sentence structure.