答案：D

题目分析：句意：他打电话告诉我,你在医院，否则我根本就不知道。这里的otherwise相当于一个虚拟条件句="if" he had’t called to tell me that you are in hospital,所以是和过去相反的虚拟语气，主句用would have done，而且根据意思应该是肯定，所以选D。