The challenge for modern states is to maintain their legitimacy while also being effective in providing services and maintaining order.

Every day is a new opportunity to change your life.

中心地的等级越高，其服务的区域越大，此类中心地的数量越少。

The boldness of his mind was matched by the candor of his speech.

下一次绿色革命必须既高效又对环境负责。