如图,将圆沿AB折叠后,圆弧恰好经过圆心,则∠AOB的度数等于( )
A:60°
B:90°
C:120°
D:150°
地球仪是地球按一定比例缩小后的模型,下列关于地球以上经线与经度、纬线与纬度的叙述,错误的是( )
The price system is a complex network composed of the prices of all the products bought and sold in the economy as well as of a great number of services.