Answer:
Option C, The particles of air move freely, colliding with each other and the sides of the balloon
Explanation:
The air molecules exert force on the inner surface of the balloon due to which the material of the balloon stretches and it increases in size. If air is blown in large extent, it will exert more force on the balloon material thereby extending it to a larger extent but when air is blown in a smaller amount, the size of the balloon increases by a smaller extent.
Hence, option C is correct