1. Mrs. Quyen does volunteer work at the hospital. She is retired teacher.
Mrs. Quyen, who is a retired teacher, does volunteer work at the hospital.
2. The man called the police. His wallet was stolen.
The man, whose wallet was stolen, called the police.
3. Last summer I spent my vacation in Sa Pa. My friend is working in it.
Last summer I spent my vacation in Sa Pa, where my friend is working.
4. The museum has just been built recently. We visited it last month.
We visited the museum that has just been built recently last month.
5. The professor is strict. We know his wife.
We know the wife of the professor who is strict.
6. The reason was unacceptable. She came late for that reason.
She came late for the reason that was unacceptable.
7. The day was terrible. I lost my job on the day.
I lost my job on the day that was terrible.
8. The hotel is luxurious. They stayed at the hotel last year.
They stayed at the hotel that is luxurious last year.

1.Mrs.Quyen who does volunteer work at the hospital is a required teacher.
2.The man whose wallet was stolen called the police.
3..Last summer I spent my vacation in Sapa, where my friend is working.
4..The museum,Which has just been built recently visited it last month.
5. The professor who is strict  know his wife.