Only 16 percent of China’s area ____ covered with forests, so ____of us should protect trees.
You have to leave now _________ you can catch the early bus.
The little elephant is afraid to go alone.He always walks _________ his mother.
—Would you like tea or coffee?—_________ is OK.I really don't mind.
Alice in Wonderland is a fantastic movie. It’s about _________.
—Who’s that man under the tree? Is it Mr Black, our new English teacher?—It_______ be. Mr Black has gone to Shanghai for a holiday. A. mustn’t B. can’t C. needn’t