如图所示，两个质量相等的物体从同一高度沿倾角不同的两个光滑斜面由静止自由滑下，到达斜面底端，则两物体具有相同的物理量是（　　）

A．下滑过程中重力的冲量

B．下滑过程中合力的冲量

C．下滑过程中动量变化量的大小

D．刚到达底端时的动量

A fire starting by spontaneous combustion can be expected in which condition?（）.

A.Paints, varnish, or other liquid flammables are stowed in a dry stores locker

B.Inert cargoes such as pig iron are loaded in a wet condition

C.Oily rags are stowed in a metal pail

D.Clean mattresses are stored in contact with an electric light bulb