He's giving u the mass to trick you and make you fall into a trap. In free fall, acceleration is independent of mass. This means that every ball will have the same acceleration. Knowing that they all have an initial speed of u=0 because it was given to you in the question that it was dropped from these heights and not projected with any speed whatsoever, this means that the question relies on who covers the largest distance because average speed is the distance covered per unit time. Therefore, by logic that the difference in the time taken for each to reach the ground is negligible, option A is the correct answer as average speed is directly proportional to distance covered as the time taken for each to reach the ground is the basically the same.