"This is the challenge we have now: to open a lot of those doors."

VOA: standard.2009.08.15

It can be challenged on normal... Yeah, open to challenge. -Right.

一般情况下人们可以挑战。,对，人们可以挑战其中的观点，-是的。

普林斯顿公开课 - 人性课程节选