The correct answer is: C. effective unit weight of soil and effective angle of shearing resistance.
The rise of water table below the foundation influences the bearing capacity of soil mainly by reducing the effective unit weight of soil and the effective angle of shearing resistance.
The effective unit weight of soil is the weight of soil per unit volume that is not supported by water. The effective angle of shearing resistance is the angle at which the soil will fail when sheared.
When the water table rises, the soil particles become saturated with water. This reduces the effective unit weight of soil because the water has weight but does not contribute to the strength of the soil.
The rise of water table also reduces the effective angle of shearing resistance because the water lubricates the soil particles and makes it easier for them to slide past each other.
As a result of the reduction in effective unit weight and effective angle of shearing resistance, the bearing capacity of soil is reduced when the water table rises.