21. Mo Yan, _______ Chinese writer, has won _______ 2012 Nobel Prize in Literature, which is _______ great surprise.
A. a; an; a B. a; the; a C. a; a;/ D. /; a; a
22. The Diaoyu Islands, ______ lie in the East China Sea have belonged to China since ancient times.
A. when B. who C. which D. what
23. The scientist decided to devote his life to _______ pollution from _______ again.
A. preventing; happening B. prevent; happen
C. preventing; happens D. preventing; will happen
