Cách chuyển câu QKĐ -> HTHT:

 - When did+ S + V-bare ..?= How long is it since S + V-qk..?

- The last time +S+ V-qk +was +tgian +(ago) 

= S +last +V-qk...

= S+ have/ has +(not)+ P2 ...+for/since + khoảng tgian/ mốc tgian..

= It's +tgian +since+ S +(last) +V-qk..?

 - S + started/ began + to-V/ V-ing ...

S + have/ has + P2 +for/since + khoảng tgian/ mốc tgian..

4.The Times was first printed two hundred years ago.

=>.It is two hundred years since The Times was first printed

5.I last saw her 5 years ago.

=> .It’s 5 years since I last saw.……..

11.My parents have been working in this factory for over 20 years.

=>Over 20 years ago since my parents worked in this factory……..

12.He has been working in this factory for 15 years.

=>.He started…to work in this factory 15 years ago…

14.We have been learning English for one year.

=>.We began learning English one year ago

15.I have been studying business administration in London for 2 years

=>.I beganstudying business administration in London 2 years ago.

40.When did he start working for the company?

=>How long ..is it since he started working for the company...?