помогите пожалуйста , дам 25 балов

1 When I opened the door, the lesson (to begin) ... and the
teacher (to explain) ... something to the class.
2 (to clean) ... the carpet when the dog (to come) ... and (to
shake) ... itself.
3 When the bell rang, the children (to run) ... into the classroom
and (to take) ... their seats.
4 We (to have) ... a good long holiday after we (to do) ... all the
work.
5 Before we (to take) ... the boy to the theatre, he (never, to
see) ... a play.
6 By the time we (to arrive) ..., the party (to finish)....
7 When I (to get) ... to the playground, my friend ... already (to
leave) ... sol (not to see) ... him that day.
8 What ... you (to do) ... when I (to call) ... you? I (to cook)....