theo mình đây đều là thì hiện tại hoàn thành nên ta có công thức

s + have / has + v-ed /v3

s + haven't / hasn't + ved /v3

have / has + s + ved /v3

. It is 4 years since we last saw him
It is 2 years since my father went to Hanoi
 It is years since I last enjoyed myself
 It is 2 years since I last ate this kind of food
 It is hours since Mary last rang
I haven’t gone to see them for over a year
 I haven’t played football for more than ten years

Samuel has kept a diary since 1997
We have been learning English for five years
 I have lived in Ho Chi Minh since I was 8
 She started teaching the children in this remote village five months ago
The last time he wrote to me was in April
She last had a swim five years ago
They haven’t talked to each other for two months
She hasn’t seen her elder sister since 1999
 It’s years since she last wrote to me
It’s ten years since Robert and Catherine got married 

1. It is 4 years since we last saw him
2. It is 2 years since my father went to Hanoi
3. It is years since I last enjoyed myself
4. It is 2 years since I last ate this kind of food
5. It is hours since Mary last rang
6. I haven’t gone to see them for over a year
7. I haven’t played football for more than ten years
8. Samuel has kept a diary since 1997
9. We have been learning English for five years
10. I have lived in Ho Chi Minh since I was 8
11. She started teaching the children in this remote village five months ago
12. The last time he wrote to me was in April
13. She last had a swim five years ago
14. They haven’t talked to each other for two months
15. She hasn’t seen her elder sister since 1999
16. It’s years since she last wrote to me
17. It’s ten years since Robert and Catherine got married