Помогите доделать упражнение на темы Past Perfect or Past Simple. Даю 30 баллов!!!!

Ответ:

1.

8) hadn't studied

12) hadn't locked

15) had never visited

2.

3) wasn't working, didn't turn it on

5) have never flown

6) couldn't, disappeared

7) just had, can't be

8) ran, didn't pay

10) lost

11) can, studied

12) was