Passive voice: past (was were+pp)

1)Nobody knew his address

2)Did the students collect stamps for the club?

3)She didn't meet him 2 years ago

4)My mother made me clean this table

5)We didn't help them for 3 years

6)Where did you buy this phone card?

7)Which subjects did they study at school?

8)He invited a lot of people to the party