出处:1892年纽约芝加哥的电话线路开通。电话发明人贝尔第一个试音时的声音，这一历史性声音被记录下来。

The sun himself is weak when he first rises, and gathers strength and courage as the day gets on.

The chemical industry is the backbone of modern civilization, and we must treat it with the responsibility it deserves.

形式验证的挑战在于弥合抽象模型与实际实现之间的差距。