1. didn't work (có last year=>chia thì QKĐ)
2. will study (có next year)
3. will learn
4. hadn't enjoyed (Before+QKĐ, QKHT)
5. was doing (While S was/were doing st)
6. noticed
7. was
8. had
9. have already begun (có already)
10. will do (quyết định ngay thời điểm nói)