解释:乌鸦聚集在一起,虽然看上去很和好,实际上并不亲密;不慎重地结交朋友,虽似牢固,终必破裂。
The key to progress in science is persistence and an open mind.
The only limits you have are the limits you believe.
经济理论提供工具,但现实世界的测试会完善它们。