You can't take the exam unless you're registered for the class, and we need to make sure we can verify that.

否则你是不能参加这次考试的,除非你注册了这门课，而我们需要确定你能证实这一点。

麻省理工公开课 - 化学原理课程节选

You can't actually register for any of those discussion section times yet.

实际上,你不能注册任何一个讨论小组。

耶鲁公开课 - 死亡课程节选