1. is
2. are they happy
3. wrote
4. doesn't go, is
5. did his brother come, he didn't come, he was busy
6. had
7. got, took
8. do you often go, we go
9. didn't notice, we were, she didn't see
10. do you like
11. did she buy, she didn't buy
12. does your sister do, meets
13. didn't understand
14. moved
15. is, ate
16. did they sell, don't know