`\color{#145277}{N}\color{#246483}{a}\color{#34768F} {e}\color{#44889B}{u}\color{#539AA7}{n}`

`***` Thì HTHT : 

`@` For `+` quãng thời gian : trong khoảng (for a month, for a long time)

`@` Since `+` mốc thời gian : từ khi (since `2006`, since `2008`)

`(+):` S + have/ has + VpII

`(-):` S + have/ has + not + VpII

`(?):` Have/ Has + S + V3 `?`

       WH-word + have/ has + S (not) + V3 `?`

`->` S = I/ We/ You/ They + have

`->` S = He/ She/ It + has 

`-------`

`1.` did you learn `-` have learnt `-` was

`2.` have they been `-` don't know `-` have been

`@` When did + S + V_bare + O `?`

`->` How long ago + did + S + V_bare + O `?`

`->` How long + have / has + S + V3 / ed + O `?`

`->` How long is it / has it been + since + S + V2 / ed + O `?`

1. did you learnt / have learnt - was

- QKĐ: S + V2 + O

- HTHT: S + have/has + VpII

- HTHT + since + QKĐ

2. have they been / don't know - have been

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

- HTĐ: S + V-s/es + O

- since 7 o'clock --> HTHT

- S + have/has VpII