1. Any student who does not want to go on the trip should inform the office. (chủ ngữ là Any student chỉ con người nên dùng who)

2. Two-third of those who are arrested for car theft are under 20 years of age. (giống câu 1)

3. Mercury, which is also the smallest of the nine planets orbiting the sun, is the nearest planet to the sun. (mercury là vật dùng which)

4. The children need a big yard in which they can play. (chủ ngữ là a big yard => which

5. He read The Old Man and the sea, which was written by Ernest Hemingway (the old man and the sea là chủ ngữ => which

6. I have some letters which I have to type right now. (some letters =>which)

7. He was the last man who left the building. (the last man => who)

8. The air-hostess was the only person who survived the crash. (the air=hostess=> who)

9. Neil Amstrong was the first man to walk on the moon. 

10. They were the most courageous people who saved the house. (the most courageous people => who)