4.-Since when have you learnt English?

-I haven learnt it since I have been a girl of twelve 

5.-have you ever been to HCM city?

-No,I haven't been there yet.But my parents have been three twice this year

6.They have done nothing since they have gotten up

7.My brother joined the army when he was 18.He have served in the army for 3 years and then have gone to university

8.How long have you lived in this town?

I have lived in this town for 10 years

9.My sister finished school in 1997 and has been a student at the National University since then

4. Since when did learn English (sau since chia Qúa Khứ Đơn)

   I have learnt it since I was a girl of twelve (sau since chia QKĐ, trước Since chia Hiện Tại Hoàn Thành)

5. Have you ever been to HCM City?  (ever, yet là dấu hiệu nhận biết của thì HTHT)

   No. I haven't been there yet. But my parents have been there twice this year.

6. They haven't done anything since they got up.

 7. My brother joined the army when he was 18. He served in the army for three years and then went to university. (Ở đây không chia thì HTHT<tuy có for> bởi vì đây là hành động đã xảy ra trong QK và kết thú rồi, ko còng kéo dài đến hiện tại  nữa)

8. How long have you lived in this town?

  I have been living/have lived in this town for ten years (chia HTHT/HTHT tiếp diễn bởi vì đây là hành động vẫn đang kéo dài tới hiện tại tuy nhiên HTHT tiếp diễn ,mang ý nhấn mạnh hơn)

9. My sister finished school in 1997(in + mốc thời gian xác định là đấu hiệu nhận biết thì QKĐ) and has been(HTHT) at the National University since then.