A student attempts to slide a block down a smooth,
dry ramp as shown, but the block does not move.
The most likely explanation is that:
A. the ramp is not steep enough for gravity to have any effect.
B.there are no forces between the block and ramp.
C. the sliding friction between the block and the ramp is lower than the force of gravity pulling the box down the ramp.
D. the static friction between the block and the ramp is greater than
the force of gravity pulling the box down the ramp.