1. I am writing an English exercise now.
2. I was writing an English exercise at this time yesterday.
3. My little sister is sleeping now.
4 My little sister was sleeping at this time yesterday.
5. My friends aren't doing their homework now. They are playing volley-ball.
6. My friends did their homework yesterday.
7. Are you eating ice-cream now?
8. Did you eat ice-cream yesterday?
9. What does your father do? (what is your father doing?)
10. What did your father do yesterday?
11. They aren't playing in the street now.
12. Are they playing in the room now?
13. He is helping his mother now.
14. Did he help his mother yesterday?
