`19,` was having

- while + QKTD : trong khi

`20,` ended

- Trong quá khứ, hành động đang diễn ra chia QKTD

- Hành động xen vào chia QĐ

`21,` invented

- a long time ago `->` Thì quá khứ đơn

- Động từ thường `(+)` S + Ved/ V2

`22,` has not spoken

- for over a month `->` Thì HTHT

- `(+)` S + have/has + PII

`23,` had broken

- QKHT + before + QKĐ

`24,` bought

- yesterday morning `->` Thì QKĐ

`25,` Have you had

- yet `->` Thì HTHT

`(?)` Have/Has + S + PII?

`26,` had gone

- After + QKHT, QKĐ

`27,` went

- QKHT + before + QKĐ

`28,` have not seen

- so far `->` Thì HTHT

- `(-)` S + have/has + not + PII

`29,` had gone

- As soon as + QKHT, QKĐ : ngay sau khi

`30,` had already see

- already `->` Thì HTHT

- S + said (that) + S + V (lùi thì)

- HTHT `->` QKHT