一Excuse me, but where’s Mrs. Liu? I want to ask her for some advice.一Shethe library. You can find her there.

This machine was used ——-years ago.

The river smells so terrible! How did it come about?—People used to pour dirty water into it.

What happened_____ your father?— He had an accident.[ ]

Let’s go _____ the road now.—Wait a moment please. The light is red now.[ ]