Ответ:

1 had

2 does, meets

3 did his brother come, didn't come, was busy

4 get, slept

5 do

6 was, became

7 didn't understand

8 do you go to the, go

9 sleeps, slept

10 walk, took

11 did she buy, she didn't buy

12 did they sell, don't know

13 is, ate

14 left

15 are