要求一个圆的周长必须知道它的请选择CBA+Z3x,y/T5V:c/i2v)}7Z*_8f7R-Z4V+j0r;\1C
A.圆周率7R-Z4V+j0r;\1C
B.圆心7R-Z4V+j0r;\1C
C.半径或直径7R-Z4V+j0r;\1C