1. He____ (study) at this school ten years ago.
2. They ____  (watch) TV at home since 8:00.
3. It's 9:00 now. All the students ____ (have) an English class in the classroom.
4. — ____ you ____ (see) any movie recently?
    —Yes, I ____ (see) Harry PotterⅢ yesterday.
5. Our English teacher ____ (teach) English at this school for about 20 years.
6. Mary's father likes ____ (climb) mountains, so climbing mountains is his hobby.
7. As drivers, they must ____ (obey) traffic rules.
8. She ____ (scream) when she saw a long snake.
9. We didn't go home until we finished ____ (clean) the classroom.
10. Do you know how ____  (make) a vegetable salad?