`-` Thì QKĐ :

`+` PĐ : S + didn't + V `-` S + wasn't / weren't + adj / n

`+` NV : Did + S + V ? `-` Was / Were + S + adj / n ?

`=>` `DHNB` : ago , last , yesterday , ...

`1`.

`( - )` My father didn't decorate the Christmas tree

`( ? )` Did your father decorate the Christmas tree ?

`2`.

`( - )` She didn't buy a new dress yesterday

`( ? )` Did she buy a new dress yesterday ?

`3`.

`( - )` They weren't late for school

`( ? )` Were they late for school ?

`\text{# TF}`

$\color{red}{\textbf{Cấu trúc QKĐ với động từ thường:}}$

`(+)` `S + V_(ed) .....`

`(-)` `S` `+` `didn't` `/` `did not` `+ V_(nt) .....`

`(?)` `Did` `/ ``Didn't` `+ S + V_(nt)` `...?`

$\color{ red }{\textbf{Cấu trúc QKĐ với động từ tobe:}}$

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

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

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

-----------------------------------------

1. My father decorated the Christmas tree.

`(-)` My father did decorate the Christmas tree.

`(?)` Did my father decorate the Christmas tree`?`

2. She bought a new dress yesterday.

`(-)` She did buy a new dress yesterday.

`(?)` Did she buy a new dress yesterday `?`

3. They were late for school.

`(-)` They weren't late for school.

`(?)` Were they late for school `?`