一幅图的比例尺是1:500000,图上距离是4厘米,它表示的实际距离是请选择CBA5v)R'S;u3x9P5S:P8^*u*m7k9L+H;j1o
A.2千米8^*u*m7k9L+H;j1o
B.20千米8^*u*m7k9L+H;j1o
C.200米8^*u*m7k9L+H;j1o