二、单项填空（共20小题，计分20分）
从A 、B、 C、 D四个选项中选出可以填入空白处的最佳选项。
( ) 21. Though my answer is different from _____, I still think _____ is right.
A. their, my B. their, mine C. theirs, mine D. theirs, my
( ) 22. _____ of them is a teacher. They are both students.
A. Neither B. Either C. All D. Both
( ) 23. A person with good manners never laughs _____ people when they are _____ trouble.
A. on, in B. in, at C. on, at D. at, in
