As is recorded in history, silkworms (蚕) were first raised by a woman in _____ is today Hebei Province.
They boy said ________ couldn’t he work out the problem but his teacher didn’t know how to do it.
She will have to find some other work for she can’t ________ this loud noise any more.
— Why weren't you at the meeting? — I ________ for a long distance call from my sister in America.
We have done things we ought not to have done and ________ undone things we ought to have done.
The two ladies are ________ the same age, but there seems to be ten years ________ them.