如图所示,一小滑块从光滑的1/4圆弧的最高点由静止滑下,滑出槽口时速度方向为水平,槽口与一个半球顶点相切,若要使小物块滑出槽口后不沿半球面下滑,则R1、R2应满足的关系是( )
A:R1≤R2
B:R1≤R22
C:R1≥R2
D:R1≥R22
Up till now, the moon is known as a (an) __________ place because nothing can live or grow there.
a+3=b+____
a÷____ =b÷20.
下列说法正确的是( )