若2弧度的圆心角所对的弧长为4cm,则这个圆心角所夹的扇形的面积是( )
A:2πcm2
B:2 cm2
C:4πcm2
D:4 cm2
Last month I travelled across the Sahara Desert by camel with some locals. What amazing experience!
下列各种单色光中,不属于三原色光之一的是( )