9. John didn't study for the exam, which was a very stupid thing to do

which thay thế cho cả mệnh đề phía trước
10. We flew to New York in the Concorde, which is the fastest passenger plane in the world

which thay thế cho từ chỉ vật
11. Smallpox, which once killed thousand of people every year, has disappeared 

which thay thế cho từ chỉ vật
12. I passed him a large glass of whisky, which he drank immediately

which thay thế cho từ chỉ vật
13. The small man whom nobody recognised was Lisa's husband 
whom thay thế tân ngữ
14. This is Mr Jones who writes poetry
who thay thế từ chỉ người 
15. This is Felicity whose sister you met last week
whose thay thế tính từ sở hữu
16. He swam across the English Channel, which is hard to believe 

which thay thế cho cả mệnh đề phía trước
17. Her wife whose name was Angela died last year  
whose thay thế tính từ sở hữu
18. Borges, who never won the Nobel Prize, was a wonderful writer
who thay thế từ chỉ người 
19. A man from our village whose children  I teach was on TV last night 
whose thay thế tính từ sở hữu
20. Charlie Chaplin, whose films amused millions, died in 1977 

whose thay thế tính từ sở hữu