3. A lot of people suffer from technostress whom work in my office .

4. The man is a computer expert whom you talked to yesterday .

5. Some documents have been found which were stolen from a car . 

6. Daisy has a brother whom is the same age as me . 

7. I will introduce the man whom is sharing the flat with me to you .

8. I'm reading a book which I bought in Sydney in 1996 .

9. This girl arrived here at 6:30 who chatted with him yesterday . 

10. The fire had started in that building which we all looked at .

3. A lot of people who work at my office suffer from technostress.

4. The man who/that you talked to yesterday is a computer expert.

5. Some documents that/which were stolen from a car have been found.

6. Daisy has a brother who has the same age as me.

7. I will introduce the man who is sharing a flat with me to you.

8. I'm reading a book that/which I bought in Sydney in 1996.

9. This girl, who arrived here at 6:30, chatted with him yesterday .

This girl: danh từ đã xác định nên có dấu phẩy trước mệnh đề quan hệ 

10. We all looked at that building, in which the fire had started. 

in which = where

that building: danh từ đã xác định nên có dấu phẩy trước mệnh đề quan hệ