Answer: Normal force prevents the cup from falling to the ground.
Explanation :
When a cup is placed on a table, the forces acting on the cup are the gravitational force and the normal force. The gravitational force acts in the downward direction while the normal force acts in an upward direction.
In the figure, N is the normal force and mg is the weight of an object acting in downward direction.
It is clear that the gravitational force is balanced by the normal force.
So, the correct option is (b) " normal force ".