I think what part of Sustain Dialogue does and just being in community with people it also challenges you. -It does.

我觉得，“持续对话“所做的部分活动,和与你不同的人在一起交流,这很有挑战性，-的确。

普林斯顿公开课 - 人性课程节选

The challenge is for the work you are going to be doing at the class time we are doing to spend together.

这一挑战是针对,我们要一起在课上,完成的任务提出的。

麻省理工公开课 - 媒体、教育、市场课程节选