1. have been studying

2. had loved - found - had cheated

3. had been working - fired

4. had been waiting - arrived

5. had - hadn't brought

6. hadn't waited - showed up

7. had been exercising - rang

8. realized - had left

dùng thì QKHT diễn tả hành động xảy ra trước hành động khác trong quá khứ

1.I ___________have been studying_______________ (study) for 5 years, so I was tired.

2.I ______________had loved____________ (love) her until I ____________found______________ (find) out that she ____________had cheated______________ (cheat) on me for a year.

3.Maria _____________had been working_____________ (work) at the company for 20 years until they _______________fired___________ (fire) her one day for no reason.

4.John ________had been waiting__________________ (wait) for Paula for 1 hour before she finally ________________arrived__________ (arrive).

5.Lisa ________had__________________ (have) trouble seeing the screen because she ___________hadn"t brought______showed up_________ (not/bring) her glasses.

6.Cheryl _____________hadn"t waited _____________ (not/wait) long when John __________________________ (show up)

7.I ___________had been exercising_______________ (exercise) for 30 minutes when the phone ______rang____________________ (ring).

8.The traveler suddenly ________realized__________________ (realize) that he _______________had left___________ (leave) home without his passport.