1. While I (walk) was walking across the campus the other day, => kết hợp thì
I (meet) met my old friend => kết hợp thì với vế trên
John, whom I (not see)haven't seen :since July 10 => có từ since => dùng hTHT
Naturally we (stop)stopped (talk) talking to each other for a few minutes. => hđ trong quá khứ nên stop chia ở QKĐ , sau stop cộng V_ing
I asked him how he (do) did in his classes this semester.
2. Jack London (bear) beared in San Francisco on January 12, 1876. => có thời gian trong qk => QKĐ
He (begin)began his education at the university of California, => hđ trong qk => QKĐ
but (not finish) hadn't finished it there,
he (write) wrote a lot of adventure books. He (travel) traveled much,
and his experience in his trips (help) helped him write many famous books.