There is a boy the bike. ( )
A:in
B:at
C:on
Sometimes children are ____ young ____ they can't tell the bad from the good.
一物体受到与它的运动方向相反的力F(x)=ex+x的作用,则它从x=0运动到x=1时,F(x)所做的功等于( )
已知A,B都是锐角、且sinA<sinB,则下列关系正确的是( )
如图,写出△ABC的各顶点坐标,并画出△ABC关于y轴对称的△A1B1C1,写出△ABC关于X轴对称的△A2B2C2的各点坐标.
地球的平均半径是( )