13. If someone doesn't put the coal in, the fire will go out. (UNLESS) 14. The girl is very friendly. She lived next door to us. (WHO) 15. He doesn't have a computer now. (WISHES) 16. It's 3 years since I last saw Nam. (SEEN) 17. It was a two-hour flight from Hanoi to Ho Chi Minh City. (TOOK) 18. We last saw our grandfather five months ago. (HAVEN’T) 19. “Where do your parents live now?” said Nam to me. (ASKED) 20. Spending our weekend in the countryside is very interesting. (IT’S) 21. Have you ever spoken to the people? They live next door. (WHO) 22. Jane can play the piano better than Bella. (WELL)

13. Unless someone puts the coal in, the fire will go out.

If not cũng có nghĩa là Unless: trừ khi

14.The girl who lived next door to us is very friendly.

15.He wishes he had a computer now

Câu ước: S + wish(es) + (that) + S + V-ed

16.I haven't seen Nam for 3 years

HTHT: S + haven't/ hasn't + V3/ed...

17. It took two hours to fly from Ha Noi to Ho Chi Minh city.

18. We haven’t seen our grandfather for the last five months

HTHT: S + haven't/ hasn't + V3/ed...

19.Nam asked me where my parents lived then 

Cấu trúc câu gián tiếp: S + asked/asked + sb/wondered/wanted to know + Clause 

20.It’s very wonderful to spend the weekend in the countryside.

Cấu trúc:  It is + adj + to V : Việc làm gì là thế nào

21.Have you ever spoken to the people who live next door ?

HTHT: Have you ever + V3/ed...

22.Bella can't play piano as well as Jane

Cấu trúc so sánh kém hơn: S1+ can't + V + N + as well as +S2