She must have gone out early,for she had not shown up at breakfast.

问题描述:

She must have gone out early,for she had not shown up at breakfast.
这个句子为什么用“must have gone”,整个句子是虚拟语气吗?虚拟语气中不是用could(should would might)+have done的形式吗?在这里为什么用must,另外翻译下这句话,

这里不是虚拟语气,而是用情态动词must表示说话人的一种比较肯定的猜测.
“她肯定一早就出去了,因为她吃早饭的时候都没出现.”