15 A: What do you think of Up? B: A It's a comedy film. B It was expensive. C It's great. You should see it.

The question asks for an opinion about the film 'Up'. Option C, 'It's great. You should see it.', provides a positive opinion and a recommendation, which is a suitable response to 'What do you think of...?'
Answer: C It's great. You should see it.