在计算学习理论中，挑战不仅仅是学习，而是理解学习是如何可能的。

A man of genius makes no mistakes. His errors are volitional and are the portals of discovery.

The future of forestry lies in balancing economic needs with ecological responsibility.

可持续性不仅仅是一个流行词；它是负责任水产养殖的基础。

目的可以证明手段的正当性，只要存在某种能证明目的正当性的东西。