Ex 3 :
1.went / had finished ( S + Ved, after + S + V(past perfect)
2.had done / saw ( S + V(past perfect),before + S + Ved)
3.thanked / had done
4.was / had hurted
5.had gone / sitted / rested
6.hadn't seen / met
Cấu trúc : S + have / has (never /not) + Vpp +.... + for /since +time
7.remmembered / learnt
8.told / hadn't met
9.asked / came ( cấu trúc tường thuật.)
10.said / had already seen