IV/
1. are / doing ? am watching ( Thì HTTD )
2. have been ( Thì HTHT )
3. listening ( spend + time + V_ing )
4. will play / to join ( Thì TLGần )
5. am not using ( Thì HTTD )
6. is flying ( Sau dấu ! thì V_ing )
7. didn't visit ( Thì QKĐ )
8. had / join ( Thì QKĐ )