1. Listen! I (think) someone _________ (knock) at the door. 2. Up to the present, we _________ (write) almost every lesson in the book. 3. The earth _________ (circle) the sun once every 365 days. 4. The farmer _________ (work) in the field at the moment. 5. Rivers usually _________ (flow) to the sea. 6. How many times you _________ (see) him since he went to London? 7. I _________ (wait) for the manager for two hours. 8. Mrs. Green always _________ (go) to work by bus. 9. Look! The boy is _________ (cry)ing. 10. You _________ (ever, see) a money?