A spherical ball is dropped in a long column of viscous liquid Which of the following graphs represent the variation of
(i)   gravitational force with time
(ii)  viscous force with time
(iii) net force acting on the bass with time

Gravitational force remains contant. Therefore, P is the correct graph for the gravitational force.

Net force acting on the ball will keep on decrease because the buoyancy force will keep on increasing as the ball achieves more and more depth. So, a time will come when the forces become equal and the ball attains a constant velocity.Therefore, R is the correct graph for the net force acting on the bass with time

And finally, viscous force will keep on increasing as the no. of layers of liquid will keep on increasing as the ball moves deeper inside the liquid.