(N/A) $(i)$ The stone falls towards the earth because of the gravitational force exerted by the earth on the stone. According to the universal law of gravitation,every object in the universe attracts every other object with a force. Since the earth is massive,its gravitational pull on the stone is significant,causing the stone to accelerate towards it.
$(ii)$ According to the universal law of gravitation,the force of attraction between two objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. Since the masses of ordinary objects in a room are very small,the gravitational force between them is extremely weak. This force is negligible compared to the frictional forces and the gravitational pull of the earth,which is why they do not move towards each other.