—David, you left your English book on the desk?—It isn’t . I think it is .
What did you do with those books given by the volunteers?
Sometimes I feel bored and don’t know ______ to do.
Helen has no friends _______.
____ Mr. Zhang gave us some good suggestions, but we still didn’t deal with those problems very well.
When we heard the good news , all of us were very ______ .