1.since-for

2.saw-seen

3.was-has been

4.interrupt-interrupting

5.didn't try-haven't tried

6.has been - was

7.enjoyed-have enjoyed

8.played-has played

9.knew-have known

10.performed- were performed

11.they-we

12.was-0

13.two days ago-for two days

14.didn't see- hasn't seen

15.participated-have participated

16.speak-have spoken

17.worked-has worked, has moved-moved

18.played-has played

19.didn't see- haven't seen

20.have-0

1. the last time we went to the concert was over a year ago

2.we haven't seen our grandfather for two years

3.this is the first time i have ever read a romantic story

4.my father has seen my uncle for nearly twenty years

5.it's over 20 years since he went backs to his village

6.we haven't felt interested since the journey to the village

7.we haven't gone to a cinema for two years

8.we haven't seen him since monday

9.i haven't seen david since 1989