1. I met a friend when I was on my way home yesterday.
2. I'm doing my homework,so I can't go to the supermarket with you .
3. I was watching TV when my mother came back.
4. The earth moves around the sun.
5. When did you go to the park?
6. I have been to China for two years.
7. Jack is going to America the day after tomorrow.
8. I studied in that school last year.
9. The train starts at 10 o'clock in the morning.
10. He said he had finished his homework.
11. I’m going to the park with my friend Lucy.
12. He said he would go to Beijing the next day.
13. What will you be doing at this time next Monday?
14. I didn't know you were so busy.
15. Spring is coming.