Those _____ sheep.
Keys _______ opening the lock in the door.
—I have never been to the Great wall. —If you have an opportunity _______ there, you must take it.
There was _____ woman in the room, sitting and looking at me in the dark.
—How do you study English so well? —I think _________ English movies is a good way to learn English.
Don’t _______ the people who are in trouble.