从A.B.C.D四个选项中，选出可以填入空白处的最佳选项。
例：It is generally considered unwise to give a child ______he or she wants.
A. however B. whatever C. whichever D. whenever
答案是B。
21. My summer camp isn’t good fun, but it is real learning experience for me.
A. a; / B. the; a C. /; a D. a; the
22. Which do you prefer, tea or coffee?
—_______. I really don’t mind.
A. Both B. None C. Neither D. Either
