10. It's ten years since Robert and Catherine were married

`->` S + have/has + VpII + for + KTG

`=` It's/It has been + KTG + since + S + (last) + V2 + O

11. They have cleaned their room for two weeks

12. John has had his hair cut for over six months

13. When did you start riding a bicycle?

`->` How long + have/has + S + VpII + O?

`=` When + did + S + start/begin + to V/V-ing

`=` When + did + S + V-bare

14. When did he start writting to you?

15. How has he talked to you?

16. How long have you telephoned him?

17. It's the first time I have eaten this kind of food

`->` This is/It's + the first time + S + have/has + VpII

`=` S + have/has + never + VpII + before

`=` S + haven't/hasn't + VpII + before

18. I have never seen this film before

`10` It's ten years since Robert and Catherine were married.

`=>` It's + khoảng thời gian + since + S + V-QKĐ: Đã bao lâu kể từ khi

`11`They haven't cleaned their room for two weeks.

`=>`S + have/has + not + Vp.p + .... + for + khoảng thời gian

`12` John hasn't had his hair cut for over six months.

`=>`S + have/has + not + Vp.p + .... + for + khoảng thời gian

`13` When did you (last) ride a bicycle?

`14` When did he (last) write to you?

`=>`When `+` did `+` S`+` (last)`+` V? (`13,14)`

`15` How long is it since he talked to you?

`16` How long is it since you telephoned him?

`=>` How long is it since`+` S`+` (last)`+` V2/ed? `(15,16)`

`17` It's the first time we have eaten this kind of food.

`=>`This is the first time `+` S`+` have/has`+` V3/ed

`18` I have never seen this film before.

`=>`S`+` have/has `+` never`+` V3/ed `+` before