—Do you have _____ trouble finishing the work?—The work is not so difficult as you think. We have finished it already.
Your English teacher looks very young; He _____ be over 30.
——Need I clean the room now? ——Yes, you _____ , but you ______ ask someone to help you.
——Don't forget to come to my birthday party tomorrow.——______.
What do you think ______ an apple ______ to the ground?
Why do you think ______ cut down the big tree?