1. A

S + said +(that) + S+ V (lùi thì)

HTTD ⇒ QKTD

now ⇒ then 

2. B

S + asked + O + if/whether + S  +V (lùi thì)

HTHT ⇒ QKHT

3. B / C 

QKD ⇒ QKHT 

yesterday ⇒ the day before / the previous day 

S + said to + O + " ......... " 

4. B

If 1: if + S +  V1/s/es, S + will/can/shall .. + V1 

5. C

S + V2/ed: thì QKĐ

`color{orange}{~MiaMB~}`