— I'm afraid I can't get to the museum on time because the traffic is too busy.
— Don't worry, Millie. I'll keep________ until you come here.
一个质量为m的物体,(体积可忽略),在半径为R,的光滑半球顶点处以水平速度v0运动,如图所示,则下列说法正确的是( )
如图,“美国东北部工业区图”和“我国京津唐工业区图”,完成下题。