`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.` were not going

`9.` was not doing

`10.` was reading `-` were playing

`___________________________`

`***` QKTD:

`(+)` S + was/were + V_ing  +  O

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

`(?)` Was/ were   + S   + V_ing +  O?

`@` DHNB:  at + giờ +  past time , at this time + past time, in + year,...

`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 - were playing

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

Giải thích:

`@` Cấu trúc quá khứ tiếp diễn:

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

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

(`?`) Was/Were `+` S `+` V-ing ..? 

`-` DHNB: at + giờ chính xác + tgian trong quá khứ, in + năm xác định,...

`-` While `+` QKTD, QKTD

`+` Diễn tả hai hành động xảy ra đồng thời, song song trong quá khứ.

`-` QKTD: S `+` was/were `+` V-ing .. 

----

`-` When + QKĐ, QKTD

`+` Diễn tả một hành động đang diễn ra thì một hành động khác xen vào.

`-` QKĐ: S `+` V2/V-ed `+` O

`-` QKTD: S `+` was/were `+` V-ing `+` O

`->` Dùng để nhấn mạnh diễn biến, tgian diễn ra, diễn tả hành động đang xảy ra tại 1 thời điểm trong quá khứ, hành động đang xảy ra thì có hành động khác xen vào, hoặc hành động lặp đi lặp lại trong quá khứ làm phiền đến người khác.