小于给定数的素数个数是该数的一个函数。

当你来自一个饱受战争摧残的国家时，你对生活会有不同的看法。

怎堪忍受花开满枝，反而引发了两地相思。

His back’s as crooked as a politician.

"Literature is the mirror of society, reflecting its virtues and vices, its hopes and fears."

我不害怕失败，我害怕不去尝试。