. They did everything they could to prevent the pollution ______ the river.

A．protecting

B．to protect

C．from being protected

D．from protecting

如图所示，重为25N的木块在大小为10N的水平拉力F的作用下，在10s内沿水平地面匀速前进5m，则物体受到的摩擦力为         N，拉力做的功为          J。