Don't make me _____ this or that. I'm too busy! [ ]
A. to do
B. do
C. doing
D. done
答案:B
用与球心O距离为1的截面去截球,所得截面的面积为9π,则球的表面积为[ ]
A、4π
B、10π
C、20π
D、40π
半径为6厘米,圆心角为150°的弧长是______厘米.