they like ice cream /Do they like ice cream?/What do they like?/They don’t like ice cream.the must go home now./ Must they go home now?/When must they go home?/They mustn’t go home now.这两段对话 为什么第一个用do 第二个不用呢?
问题描述：
they like ice cream /Do they like ice cream?/What do they like?/They don’t like ice cream.
the must go home now./ Must they go home now?/When must they go home?/They mustn’t go home now.
这两段对话 为什么第一个用do 第二个不用呢?
答