1. We began eating when it started to rain.

   He hasn't ................................

2. I last had my hair cut when i left her.

   I haven't ..................................

3. When did you have it ?

   How long .................................?

`1,` He has eaten since it started to rain (Sửa : hasn't -> has)

- S + started/began + to V/V-ing + when/in/on/at + thời gian

= S + has/have + Vpp + since/for + thời gian

- since + mốc thời gian 

`2,` I haven't had my hair cut since I left her.

- S + last + Ved/V2 + O + when/in/on/at + thời gian

= S + has/have + not + Vpp + since/for + thời gian 

- since + mốc thời gian

`3,` How long is it since you had it?

Hoặc : How long have you had it?

- When + did + S + V-inf + O ?

= How long is it since + S + Ved/V2 + O?

= How long + has/have + S + Vpp + O? 

`color{red}{#Atr}`

`1.` He has eaten since it started to rain.

`-` S + began/started + V-ing/to V-bare + times ago/in time

`=` S + have/has + Vp2 + for times/since time

`-` since + mốc thời gian

`2.` I haven't had my hair cut since I left her.

`-` S + last + QKĐ + times ago/in + time

`=` S + have/has + not + Vp2 + for times/since time

`-` since + mốc thời gian

`-` Bị động với "have": have sth done (by sb): nhờ ai làm gì (nhờ vả)

`3.` How long have you had it?

Hoặc: How long is it since you had it?

`-` When + did + S + V-bare + O?

`=` How long + have/has + S + Vp2 + O?

`=` How long is it + since + QKĐ?