---The TV is too noisy, would you mind        a little, please?    ---Sorry, I will do it right away.

A．turning it off

B．turning it on

C．turning it down

D．turning it up

直径为D的圆柱形桶内放入两个直径为d(2d > D > d)的光滑圆球,如图所示,其中只与球的重力有关而与桶的直径D无关的力是

A．球对桶底的压力

B．下面的球对桶侧面的压力

C．上面的球对桶侧面的压力

D．上球对下球的压力