— Where is Millie? — She ______ a trip in her room.
—How many students are there in the classroom?—_____ I don’t know where they have gone.
The rubbish _____ is produced every day is becoming a serious problem in cities around the world.
More and more trees were cut down. _____, many animals are dying out.
We should often keep _____ touch with each other, because we are good friends.
—Do you think a radio is useful in learning English?—Sure. A radio can _____ listening English songs and reports.