19. Look out! Don’t get too close to the house of which roof is under repair. 　

18. The students and things which you spoke of are known to us.

17. Which is known to all, many satellite are going around in the sky.

16. The third place which we are going to visit is Hangzhou.　

15. Taiwan, that we know, belongs to China.　　　

14. That was the reason because she looked old.　

13. Those at the desk want to buy tickets write down your names.

12. The reason which he explained it sounds reasonable.

11. We heard the news which our team won the game.　

10. Soon they came to a farm house, and in front of which sat a small boy.