`1.` Jack is having a video conference with his colleagues in Asia at the moment

`-` at the moment`-` HTTD

`-` HTTD: `(+)` S + am/is/are + V_ing + O

`2.` He said that he was doing well in science at school then

`-` Câu gián tiếp:
S + said + (that) + S + V(lùi thì)

`-` lùi thì: HTTD `-` QKTD

`-` now `-` then

`3.` Nick asked the professor why homans couldn't live on Mars

`-` Câu gián tiếp dạng Wh_question:
S + asked + O + Wh_ + S + V(lùi thì)

`-` can `-` could

`4.` Robots will replace human in 30 years'time 

`-` TLĐ: `(+)` S + will + V_inf + O

`5.` Many students asked me what differences Mars and Earth were

`-` lùi thì: HTĐ `-` QKĐ

1.Jack is having a video conference with his colleagues in Asia at the moment.

 at the moment là DHNT của HTTD

2. He said that he was doing well in science at school then

Câu gián tiếp:
S + said + (that) + S + V(lùi thì)

3.Nick asked the professor why humans cannot live on Mars.

Câu gián tiếp dạng Wh_question:
S + asked + O + Wh_ + S + V(lùi thì)

4.Robots will replace human in 30 years'time 

in 30 year time => TLĐ

5.Many students asked me what the differences between Mars and Earth were