在计算学习的背景下，“可能近似正确”（PAC）学习的概念为理解学习算法的效率和可行性提供了一个框架。
In the context of computational learning, the concept of 'probably approximately correct' (PAC) learning provides a framework for understanding the efficiency and feasibility of learning algorithms.
We must, however, acknowledge, as it seems to me, that man with all his noble qualities still bears in his bodily frame the indelible stamp of his lowly origin.
闹市是赚钱的地方，安静的地方才能休养身体。