Công thức thì HTHT

(+) S + has/have + V3/ed 

(-) S + has/have + not + V3/ed 

(?) Has/Have + S+ V3/ed?

DHNB: before, since + mốc thời gian, for + khoảng thời gian, yet, already, just,....

Công thức thì QKĐ (V: thường)

(+) S + V2/ed 

(-) S + didn't + V1 

(?) Did + S+ V1?

DHNB: ago, last (year, month ...), yesterday, in + năm QK, ...

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

1. has waited 

DHNB: for two hours (HTHT) 

2. has been

3. has seen

DHNB: several times (HTHT)

4. have lived 

DHNB: for a long time (HTHT)

5. hasn't spoken 

DHNB: since last week (HTHT)

6. have studied 

DHNB: so far (HTHT)

7. have had 

DHNB: this winter (HTHT)

8. has worked 

DHNB: up to now (HTHT)

9. sold 

DHNB: ago (QKD)

10. has worked

DHNB: since 1980 (HTHT)

11. has worked

DHNB: for two years (HTHT)

12. have seen 

DHNB: several times (HTHT)