15. The bed was comfortable . I slept in it last night

=>The bed in which I slept last night was comfortable.

16. Marie Curie was a French Physicist. Her discovery of radium is famous throughout the world.

=>Marie Curie was a french physicist who discovered radium is famous throughout the world

17.I don’t remember the day. I left school on that day.

=> I don't remember the day when I left school

18. She is the most intelligent woman. I’ve ever met this woman.

=>She is the most intelligent woman whom I’ve ever met .

19. My brother came to see us. He is in the army.

=>My brother who came to see us is in the army

20. The strike at that factory is over now. It lasted three days ago.

=>The strike at that factory which lasted three days ago is over now

21.Professor Johnson is to visit the university next week. I have long admired him

=>Professor Johnson whom I have long looked up to is to visit the University next week

22. Can you understand the question? He asked you the question last time.

=>Can you understand the question which he asked you last time?

23. Is that the girl? We saw her on T.V last night.

=>Is that the girl whom we saw on TV last night ?

24. The farm produces milk. We visited it last Sunday.

=>The farm which we visited last Sunday produces milk

25. At last he married the girl. He loved her.

=>At last he married the girl whom he loved

26. The man is an engineer. We play with his daughter everyday.

=>The man whose daughter we play with everyday is an engineer

27. He didn’t receive the letter. I sent him the letter last January.

=>He didn ' t receive the letter which I sent last January

28. He often tells me something about his village. He was born there.

=>He often tells me something about his village where he was born

29. The children like the funny stories. Their grandmother tells them those stories every evening.

=>The children like the funny stories which their grandmother tells them every evening

30. Jack London is a famous American writer. He wrote “Iron heel”.

=>Jack London,who wrote “Iron heel “,is a famous American writer

31.Our teacher assigned us the homework. We had to finish it within a week.

=>Our teacher assigned us with the homework which we had to finish within a week

32. Ngoc has just moved to a new school. It was built two years ago

=>Ngoc has just moved to a new school which was built two years ago

33.The man is selling lottery tickets. He used to be very rich

=>The man who used to be very rich is selling lottery tickets

34.Hai’s friend is a very interesting boy. He came from Da Nang.

=>Hai's friend who came from Da Nang is a very interesting boy

35. This is the boy . Her sister studied with me in high school

=>This is the boy who studied with me in high school

36. You can’t enjoy hiking in winter. Snow covers everything in winter.

=>You can't enjoy hiking in winter when snow covers everything.

37. She was born in Malaysia. Rubber trees grow well there .

=>She was born in Malaysia where Rubber trees grow well

38. No one knows the school. My uncle taught at that school 10 years ago.

=>No one knows the school which My uncle taugh 10 years ago

39. There are many seaside resorts. Tourists can enjoy their holidays there

=>There are many seaside resorts where tourists can enjoy their holidays

40. Please ask them the time. The train started the trip at that time

=>Please ask them the time when the train start the trip.

41. New Year’s Day is a day. All family members gather and enjoy a family dinner then

=>New Year's Day is the day when all family members gather and enjoy a family dinner 

42. That man is handsome. I like his lifestyle so much.

=>That man whose lifestyle i like so much is handsome

Cho mih xin ctlhn nha edit so long ;((