D. goes over
Feedback go over - 1. to think about something seriously 2. to study/examine 3. to repeat.
keep back - 1. not to tell something you know 2. not to show your emotions 3. not to give something you're supposed to give.
knock around - 1. to hit a few times 2. to spend time without any aim 3. to travel 4. to discuss something.
hit on - 1. to come across an idea/ discover something 2. to flirt