16. what it used to be

15. could have taken

14. whatever help he can get

13. which makes the others unhappy

12. one I will always treasure

11. more and more forests destroyed

20.　 pretend to be looking at something else

(20) 参考答案

19.　 to live up to

18.　 Losing her new bike

17.　 whose cover / the cover of which is broken