Viết lại câu sử dụng mệnh đề quan hệ: 1. A friend of mine, Judith Nelson, is working at an electronics firm. 2. We watched a very long but interesting play last night. 3. Our school has more than 500 students

1. A friend of mine, Judith Nelson, is working at an electronics firm
-> Judith Nelson, who...........
2. We watched a very long but interesting play last night.
-> The play which.......
3. Our school has more than 500 students
-> The school which......
-> The school where.......
-> We.....
4. They went to a concert performed by a German orchestra.
-> The concert which....
5. Her second book was very popular and became a best-seller
-> Her second book, which.....