Ex `4`

`1` Did

`2` didn't

`3` Was

`4` wasn't

`5` did

`6` Did

`7` were

`8` didn't

`9` didn't

`10` Was `-` wasn't

Ex `5`

`1` 

`(-)` Children didn't plant more trees.

`(?)` Did children plant more trees?

`---------------`

`***` Quá khứ đơn

`-` Với tobe

`(+)` S + was/were

`(-)` S + was/were + not

`(?)` (Wh) + Was/Were + S?

`-` He, she, it, N số ít + was

`-` You, we, they, N số nhiều + were

`-` I + was trong câu khẳng định và phủ định, + were trong câu nghi vấn

`-` Với động từ thường

`(+)` S + V2/ed

`(-)` S + didn't + V

`(?)` (Wh) + Did + S + V?

`->` DHNB: yesterday, this morning, in the past, last + mốc thời gian, khoảng thời gian + ago, in + năm trong quá khứ,...