A: where was it that
B:that was it where
C:where it was that
D:that was it where
一个圆形花池中央有一根旗杆,这个圆形花池的周长是94.2米,那么圆中的路长多少米?
已知质量分布均匀的球壳对其内部物体的引力为零,设想在地球赤道正上方高h处和正下方深为h处各修建一绕地心的环形真空轨道,轨道面与赤道面共面,两物件分布在上述两轨道中做匀速圆周运动,轨道对它们均无作用力,设地球半径为R,则( )
下列关于土耳其海峡、巴拿马运河表述错误的是( )