1) When I came home yesterday, my sister had already returned and watched TV
2) He smoked 3 cigarettes, looked at all the books on the shelf when he finally heard the footsteps of a friend approaching the door
3) She is going to read the letter she just received
4) He has been writing an essay for 2 hours already. He says that he will soon finish writing an essay, since he is now writing a conclusion
5) When I left the house I remembered that I forgot an umbrella at home
6) Students write a test for dinner
7) Students will write a test for dinner