Why Does Raising the Groundwater Level Often Lead to Slope

Why does raising the groundwater level often lead to slope failure?

A) It lubricates the ground, making it slide easier.
B) It creates a layer of water that the slope slides on.
C) It increases the water pressure in the pore spaces between the grains, pushing them farther apart.
D) When the ground freezes, the water turns to ice, making it slide easily.
E) The water seeps out of the ground, and the slope above slides on it.