The rise of water table below the foundation influences the bearing capacity of soil mainly by reducing:

b) cohesion and effective unit weight of soil

I would say answer A and C

The right answer  I think is  a) that is cohesion and effective angle of shearing resistance

c) effective unit weight of soil and effective angle of shearing resistance

a) cohesion and effective angle of shearing resistance

b) >>>>>>>>>>>>>>cohesion and effective unit weight of soil