11. Last week, we ____________(have) dinner with a French family.

→ had

Dấu hiệu ''Last'' -> dùng QKĐ 

Công thức QKĐ:  

Đối vs to be: S + was/ were + O

Đối vs động từ thường: S + V-ed/ V_{QK (bất quy tắc)} + O

Câu hỏi: Did + S + V

Phủ định: S + did not + V

12. In the past, ao dai ____________(wear) by both men and women.

→ was worn 

Dấu hiệu: ''In the past'' ⇒ dùng thì QKĐ
13. The Saint Giong Festival ____________(hold) many years ago but it officially ____________(become) a national festival in the 11th century.

→ was held/ became 

Dùng thì QKĐ
14.  The local authority ___________(arrange) a meeting on promotion of the festival last Friday.

→ arranged

Dấu hiệu ''last'' ⇒ dùng QKĐ
15. While we ____________(play) some folk games at the festival, it started to rain heavily.

→ were playing

While nói về 2 hành động xảy ra cùng 1 lúc với nhau. (kéo dài trong một khoảng thời gian nào đó)

Cấu trúc: While + S + QKTD, S + QKĐ +....

16.  Duong recommended Peter ____________(attend) the Hue Festival.

→ to attend 
17.  Before Tet, women are very busy ____________(prepare) traditional foods.

→ preparing

Busy + V-ing
18. Sam _____________(play) his guitar at half past seven last night

→  was playing

19. ________ you ________(drive) to work when the accident happened?

→ were/ driving

When nói về chuỗi các hành động xảy ra liên tiếp nhau

Cấu trúc: S + QKTD +.... + When + S + QKĐ
20.  It _____________(rain) on Monday so we didn’t play football.

→ was raining