Pakistan has approached the United Nations after India __ to revoke the Indus water treaty.

Pakistan moved to the United Nations after some action on India’s part. India told to revoke means that India told someone else to revoke the treaty. This is not the message which is being conveyed by the sentence. Hence option A is wrong. As the action has occurred in the past, the missing verb must be in the past tense. So option B is also wrong. Option D is also wrong as ‘talked to’ should be followed by the some party with which the discussion is going on. Thus, the correct answer is option C.