7. was watering - were playing ( while + QKTD )
8. to listen - going ( used + to- V ; before + Ving )
11. rained - were going ( thì QTĐ kết hợp với thì QKTD, dấu hiệu: while )
12. has worked ( HTHT )
18. paying - gave ( remember + V-ing: nhớ đã làm gì )
19. finding - was stolen (give up + Ving: từ bỏ làm gì ; câu bị động của thì QKĐ )
20. were leaning - are having - could not attend
22. was having - got ( thì QTĐ kết hợp với thì QKTD, dấu hiệu: when )
