tom might have come to school in time for the lecture()
tom might have come to school in time for the lecture() A if he got up earlier B unless he had got up earlier 不是有句型是:当主句是S+might have done 从句就用If+S+had done 那A是不是差个had (if he had got up earlier)
原句的意思是:汤姆也许会及时赶到学校去听演讲. A的意思是:如果他早点起床 B的意思是:除非他做点起床(unless=if not ,即为如果他没有早点起床) 按照语法来说,这是虚拟语气,所以应选A.不考虑意思,则如果要选B,此句应为tom would have come to school in time for the lecture unless he had got up earlier.因此应选A.