In our classroom, the pupils work in groups, helps them to learn to co-operate, to share

In our classroom, the pupils work in groups, helps them to learn to co-operate, to share and to develop leadership skill.
A. which
B. that
C. who
D. what

(答案→)A. whichB. thatC. whoD. what解析：考查非限制性定语从句中关系词的选择，故排除B、D两项，先行词是前面的整个句子。

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