表示对过去的猜测:must have done: 肯定已经做了什么事。 the cat must have eaten the fish. 猫一定已经把鱼吃了。
must do : 必须作某事。 i must finish my homework tonight. 今晚我必须完成家庭作业。
must have done 是虚拟语气,就是你说的对过去的猜测
must have done表示对过去的猜测
must do对现在的猜测
nust have done对现在的猜测
must do表示必须做某事,没猜测之意
must have done是对过去的猜测.