1. They (come) came  back home after they (finish) had finish their work.
 +trước AFTER dùng thì QKD , sau AFTER dùng thì QKHT

2.She said that she ( meet)had met Mr. Bean before.
 +trước BEFORE  dùng thì QKHT

3.Before he (go) went to bed, he (read) had read a novel.
 +sau BEFORE  dùng thì QKD , vế sau sử dụng thì QKHT

4.He told me he (not/wear) hadn't worn such kind of clothes before.
 +trước BEFORE dùng thì QKHT

5. When I came to the stadium, the match (start) had started
 +sau WHEN dùng thì QKD , vế sau dùng thì QKTD

6. Before she (listen) listened to music, she (do) had done homework.
 +sau BEFORE dùng thì QKD , vế sau dùng QKHT

7. Last night, Peter (go) had gone to the supermarket before he (go) went home.
 +trước BEFORE dùng thì QKHT , sau BEFORE dùng thì QKD


8.By the time he (arrive) arrived his school , all his classmates (go) had  gone out for ...
 +sau BY THE TIME dùng thì QKD , vế sau dùng thì QKHT

          *Thì QKD : (+)S+V(ed, p2)
                             (-)S+didn't + V(ed, p2)
                             (?)Did + S + V?

            *Thì QKTD: (+) S+was/were + V-ing
                                (-) S+was/were not +V-ing
                                (?) Was/were + S + V-ing 
               *Thì QKHT : (+) S+had +P2
                                    (-) S+hadn't +P2
                                    (?) Had + S +P2