1. D (buys ⇒ bought)

HTHT + since + QKĐ

QKĐ: S+ V2/ed 

2. A (didn't drink ⇒ hasn't drunk)

HTHT + since + QKĐ

HTHT: S + has/have+  V3/ed 

3. C (when ⇒ since)

HTHT + since + QKĐ

4. C (tried ⇒ has tried)

This / it is the first time + S + has/have+ V3/ed 

5. C (since ⇒ for)

for + khoảng thời gian 

6. B (will ⇒ would)

S + said+ (that) + S+ V (lùi thì)

will ⇒ would 

tomorrow ⇒ the next day / the following day 

7. D (following day ⇒ the following day) 

S + said+ (that) + S+ V (lùi thì)

will ⇒ would 

tomorrow ⇒ the next day / the following day 

8. D (last night ⇒ the night before / the previous night)

S + said+ (that) + S+ V (lùi thì)

QKD ⇒ QKHT 

last night ⇒ the night before / the previous night 

9. C (is ⇒ was)

S + told + O + (that) + S+ V (lùi thì)

DHNB: soon (HTTD)

HTTD ⇒ QKTD

10. C (have met ⇒ met)

HTHT + since + QKĐ

QKĐ: S+ V2/ed 

11. A (has bought ⇒ bought)

DHNB: yesterday (QKD)

S + V2/ed 

12. C (was ⇒ has been)

DHNB: since (HTHT)

S + has/have +V3/ed 

`color{orange}{~MiaMB~}`