朗兰兹纲领是对数学知识边界的挑战。
The Langlands program is a challenge to the boundaries of mathematical knowledge.
作家是一个必须生活在世界上但不属于它的人。
拍卖理论的挑战在于平衡简洁性和策略复杂性。
You pray for rain, you gotta deal with the mud too. That's a part of it.