Combine each pair of sentences into one, using a suitable Relative Pronoun

Combine each pair of sentences into one, using a suitable Relative Pronoun.
38. The boy is a friend of mine. You are using his dictionary.
39. The people were nice. We visited their house yesterday.
40. I like the house. Its walls were made of glass.
41. The woman is my sweetheart. I understand her the best.
42. The friends went to Canada. I worked with them last year.
43. The things are strange to me. He is talking about them.
44. Vietnam is the country. I was born there.