`1.` When I saw an accident, I was waiting for the taxi.

`-` CT: S1 `+` was/were `+` Ving `+` when `+` S2 `+` Ved/c2

`=` S2 `+` Ved/c2 `+` while `+` S1 `+` was/were `+` Ving

`->` Diễn tả một hành động đang diễn ra thì có hành động khác chen ngang

`2.` While people were talking about the earthquake, he was reading a book.

`-` CT: S1 `+` was/were `+` Ving `+` while `+` S2 `+` was/were `+` Ving

`->` Diễn tả hai hành động cùng diễn ra song song trong quá khứ

`3.` While we were running in the park, Mary fell over.

`-` Tương tự câu `1`

`4.` While she was painting a picture, her mother was making a cake.

`-` Tương tự câu `2`

`1.` I saw an accident when I was waiting for the taxi

`2.` People were taking about the earthquake while he was reading a book

`3.` We were running in the park while Mary fell over

`4.` She was painting a picture while her mother was making a cake

`_` `_` `_` `_` `_` `_` `_` `_` `_`

S `+` was/were `+` V-ing `+` when, S `+` Ved `/` P_II

S `+` was/were `+` V-ing `+`  while, S `+` was/were `+` V-ing