题目内容：

Mother hasn't come back yet
- Mother hasn,t come back yet.
-- Well,she ought ____.
A.to B.to be C.to do D.to have
为何为D.

优质解答

ought to do sth表示应该做某事
这里ought to have 就是ought to have come back,表示妈妈按理由应该已经回来了.