`1.` were building

`2.` was driving

`3.` was chatting/was teaching

`4.` was watching

`5.` was preparing

`6.` were you doing

`7.` were you going

`8.` weren't going

`9.` wasn't doing

`10.` was reading/was playing

`@` Kiến thức thì quá khứ tiếp diễn : 

`-` Khẳng định : S + was/were + V-ing + .....     

`-` Phủ định : S + was/were not + V-ing + .....

`-` Nghi vấn : Was/were + S + V-ing ?

`-` Dấu hiệu : when , while ( hành động đang diễn ra / hành động khác chen ngang ) , at this time yesterday ....

`1.` were building (DHNB : at this time last year)

`2.` was driving (Câu `4, 8, 9, 7`)

`-` Thì QKTD + when + S + Thì QKĐ

`->` Diễn tả hành động đang xảy ra trong quá khứ thì một hành động khác xảy ra chen vào.

`3.` was chatting - was teaching (Câu `10`)

`-` Thì QKTD + while + Thì QKTD

`->` Diễn tả hành động đang xảy ra song song trong qk. 

`4.` was watching  

`5.` was preparing (DHNB : at this time yesterday)

`6.` were `...` doing (DHNB : at `8` p.m yesterday)

`7.` were `...` going  

`8. weren't going  

`9.` wasn't doing  

`10.` was reading - was playing 

`@` Cấu trúc thì Quá khứ tiếp diễn

`(+)` S + was/were + V-ing

`(-)` S + wasn't/ weren't + V-ing

`(?)` (Wh-words) + was/were + S + V-ing

`-` Chủ ngữ: "I/He/ She/ It/Danh từ số ít" `->` đi với tobe "was"

`-` Chủ ngữ: "We/You/They/ Danh từ số nhiều" `->` đi với tobe "were"