1. nick (to do) his homework by seven o'clock yesterday. 2. you (to help) your father tomorrow? 3. when nick (to come) home yesterday, his mother (to return) and (to cook) dinner in the kitchen. 4. when i (to go) to school yesterday, i sud¬denly (to remember) that i (to forget) to take my english exercise book. 5. yesterday grandfather (to tell) us how he (to work) at the factory during the war. 6. when mr. and mrs. smith (to arrive) home, they (to discover) that someone (to break) into their house. 7. the man (to get) off the bus without paying while the conductor (to collect) fares upstairs.

1.Nick did his homework by seven o'clock yesterday. 
2. Will you help your father tomorrow?
3. When Nick came home yesterday, his mother has returned and cooked dinner in the kitchen.
4. When I went to school yesterday, I suddenly remembered that I have forgot to take my English exercise book.
5. Yesterday grandfather told us how he has been working at the factory during the war.
6. When Mr. and Mrs. Smith have arrived home, they discovered that someone has broken into their house.
7. The man got off the bus without paying while the conductor has been collecting fares upstairs.