一个半径是r的半圆形纸片，它的周长是 请选择DCBA.m)D)T-C-r1l3P4S/v5O1T9`:O3P,^(C-W0M7s*f,g-W4f+f
A．πr2:O3P,^(C-W0M7s*f,g-W4f+f
B．πr:O3P,^(C-W0M7s*f,g-W4f+f
C．πr+ 2r:O3P,^(C-W0M7s*f,g-W4f+f
D．πr2÷2:O3P,^(C-W0M7s*f,g-W4f+f