问题描述: He must be playing computer games at home,isn't he,为何用isn't he? 1个回答 分类:英语 2014-10-22 问题解答: 我来补答 别因为看到must而用了mustn't(禁止)因为这句的主干是“He is playing ."而must只是表示肯定的判断,不影响主句意思.所以用isn't he.例:You must know the truth,don't you? 展开全文阅读