Did you enjoy the film you saw last night?
______. I just did it for a change, as I was tired from working all day.
A. Not likely B. Not really C. Not necessarily D. Not exactly
Both B and D seem OK and I prefer D but I don't know if it is right.
D is not impossible, but unlikely. If it were used, there would normally be some addition, such as, "Not exactly, though I can't really say that I didn't enjoy it. It had some good moments". Even here, B is a more natural response, in my opinion.