A:Being absorbed
B:To absor
C:Absorbing
D:Absorbed
已知一个半径为6的扇形面积是4π,则这个扇形的圆心角是( )
— will you ask for help when you get into trouble? —My parents, I think.
呼吸系统中的哪个结构特点与肺泡与血液内的气体交换无关( )