1 could you open the window please =>would you mind ................................................................. 2 they cleaned the school yards yesterday =>the school yards ......................................

`1` Could you open the window please ? 

`->` Would you mind opening the window ? 

`-` Could + S + V-inf + O ? 

`-` Would you mind + V-ing ? 

`2` They cleaned the school yards yesterday 

`->` The school yards were cleaned yesterday 

`-` Chủ động thì Quá Khứ Đơn : S + Ved/V2 + O 

`-` Bị động thì Quá Khứ Đơn : S + was/were + Vpp + ( by O ) 

`-` They là chủ ngữ ko xác định `->` ko cần dùng by O 

`-` The school yards là số nhiều `->` chia were