`1` The english grammar was explained by our teachers last week.

`=>` Bị động QKD

`(+)` S + was / were + Vpp

`(-)` S + wasn't / weren't + Vpp

`(?)` Was / were + S + Vpp ?

`-` The English grammar số ít nên `+` was

`DHNB`: last week

`=>` The English grammar was explained by our teachers last week

`=>` Bị động thì quá khứ đơn : 

`-` S + was / were + Vpp + ( by + O ) 

`**` Trạng từ chỉ thời gian luôn đứng sau " by + O " 

`-` Tạm dịch : Ngữ pháp tiếng anh được giải thích bởi giáo viên của chúng tôi tuần qua