`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