FIXED PREPOSITIONAL phrases given below:by the dint of, the ball is in your court, come in contact with something, by the dozen, owing to, on a trip, for a change, etc.For example:I've helped him in every way I can – the ball's in his court now.The phrase 'the ball is in your court' means it is time for SOMEONE to deal with a problem or make a decision because other people have ALREADY done as much as they can.Thus the 3rd option is the correct choice as per the phrases given above. Correct Sentence: The ball is in your court.