21. Unless someone waters this tree, it will die soon. (If not = Unless)

22. We haven't met for years.

23. Tam didn’t finish her work so quickly as me.

24. Although it snowed heavily, the explorers managed to walk to the village.

25. He will be sent abroad by his parents. (Câu bị động với thì TLĐ.)

26. She said (that) she wanted to send her son to a university in the UK.

27. If Hoa didn't eat too much chocolate , she wouldn't be fat.

28.  They have never experienced the wonderful feeling in space before.

( Cấu trúc: This is the first time + S + have/has + P2
=> S +have/has + never + P2 + before )

29. Life in the city is more stressful than life in the countryside.

30. In spite of his bad cold, Minh still went to school.

(Although S +V ---> In spite of/ Despite N/NP )

21. If no one waters this tree, it will die soon.

⇒ Unless someone water this trees, it will die soon.

22. It’s years since we last met.

⇒ We haven't met her for years.

23. I finished my work more quickly than Tam did.

⇒ Tam didn’t finish her work as quickly as I did.

24. Despite the heavy snow, the explorers managed to walk to the village.

⇒ Although the snow was heavy, the explorers managed to walk to the village.

25. His parents will send him abroad.

⇒ He will be sent abroad by his parents.

26. “I want to send my son to a university in the UK”, she said

⇒ She said that she wanted to send her son to a university in the UK.

27. Hoa is fat because she eats too much chocolate.

⇒ If Hoa didn't eat too much chocolate, she wouldn't fat.

28. This is the first time they have experienced the wonderful feeling in space.

⇒ They have never experienced the wonderful feeling in space until now.

29. Life in the countryside isn’t as stressful as life in the city.

⇒ Life in the city is more stressful than life in the countryside.

30. Although Minh had a bad cold, he still went to school.

It spite of having bad cold, Minh still went to school.