试题题干
When left alone in the room, the students who did not know which ones would shock them clicked more pens and incurred more shocks than the students who knew what would happen. 请问划线部分是什么句子成分（ ）。
参考答案
正确答案：
试题解析
本题考查定语从句。
由题干中所给的句子可知，who did not know which ones would shock them 是定语从句，用来修饰前面的先行词students；who knew what would happen同样是定语从句，修饰前面的先行词students；students指人，所以关系代词用who，且在从句中作主语。故题干中划线部分是定语从句。
句意：当他们独自在房里时，相较于对情况了如指掌的学生，那些不知哪些笔带电的学生按下了更多的笔头，也感受到了更多的电击。