Correct option is B
The correct answer is (b) A pair of balanced forces acts on it.
Regarding the force(s) acting on a box of mass 500g lying on a horizontal table, the correct statement is:
(b) A pair of balanced forces acts on it.
In this scenario, the gravitational force acting downwards is balanced by the normal force exerted by the table upwards, resulting in a state of equilibrium where the forces are balanced.