`1.` I have been cleaning the floor for three hours.

`@` S + began / started + to V/ V-ing + time ago : bắt đầu làm gì

`= ` S + have/has + P2 / been Ving+ for / since ...

`2.` Stamps have been collected by Hoa since 2021

`@` CBĐ : S + have/has been + V3/P2 by O + time

`3.`

`+` Do you mind if I play soccer with you?

`+` Would you mind if I played soccer with you?

`@` Do you + mind if S + V hiện tại ? : bạn có phiền nếu ...?

`@` Would you mind if S + V quá khứ? : bạn có phiền nếu ...?

`5.` It's (very) fun to learn English

`@` It’s adj (for Sb) to do sth: Như thế nào với ai để làm gì

`=` Doing sth be ADJ (for sb)

`6.` Mai said that she would see her the next Sunday.

`@` Câu gián tiếp : S + said ( that ) S + V ( đổi ngôi/lùi thì )

`+` will `->` would 

`+` I `->` she

`7.` Minh said that they could play tennis well.

`@` Câu gián tiếp : S + said ( that ) S + V ( đổi ngôi/lùi thì )

`+` can `->` could

`+` we `->` they