If this is a multiple choice question for English learners then the correct answer will almost certainly be C. B is wrong because it is only a suggestion and the tone of this piece is that the recommendation is that Mike stop playing computer games. D is wrong because you can't end the sentence with 'need' - it would have to be 'need to'. While many native speakers would say that, and also say A - 'have to' I suspect that the examiners would disapprove of ending a sentence with a preposition (or whatever 'to' is called when it comes at the end of a sentence!), so that rules out A, which leave C.

have to / must / need to = are all correct (must) denotes a stronger obligation than have to or need to