ANS:D - none of these.

1. "A rubber ball when strikes a wall rebounds but a lead ball of the same mass and velocity when strikes the same wall, falls down": This statement describes the difference in behavior between a rubber ball and a lead ball upon striking a wall. It may or may not be true depending on various factors such as the elasticity of the rubber, the material of the wall, and the environment. Therefore, it could potentially be correct in certain situations but not universally applicable.
2. "Rubber and lead balls undergo equal changes in momentum": This statement refers to the change in momentum experienced by rubber and lead balls when they strike the wall. In reality, the change in momentum depends on various factors such as the mass, velocity, and elasticity of the balls, as well as the material and rigidity of the wall. Therefore, this statement might not always be accurate.
3. "Change in momentum suffered by the lead ball is less than that of the rubber ball": This statement suggests a comparison between the change in momentum of a lead ball and a rubber ball upon striking the wall. While this comparison may hold true under certain circumstances, it is not universally accurate due to the factors mentioned earlier.
4. "Momentum of rubber ball is less than that of lead ball": This statement compares the momentum of a rubber ball to that of a lead ball. The momentum of an object depends on its mass and velocity. Without specific information about the mass and velocity of the rubber ball and the lead ball, we cannot determine whether this statement is true or false.