By the time + QKĐ, QTHT (hành động ở QKĐ đã xảy ra trước)
After + QKHT, QKĐ (Hành động xảy ra sau 1 hành động trong quá khứ)
Before + QKĐ, QKHT (Hành động xảy ra trước 1 hành động trong quá khứ)
1.After he had found a job in a steel mill, he had got married.
Before he got married, he had found a job in a steel mill.
2.✔
3.By the time we bought souvenir for our friends, we had come back from Korean.
Before....✔
4.By the time we had a look around the shops, we had had snack,
Before we had a look around the shops, we had had snack.
After we had snack, we had had a look around the shops,
5.✔
6.John was not strong enough to go to work yesterday.
7.✔
8.My father allowed me to use his car.
9.It took us five hours to get to London.
