A cricketer moves the hands backward while catching a fast ball because doing so

The correct answer is B. Whether the hands are moved or not, the momentum of the ball must be brought down to zero. By the second law of motion the force is the change of momentum divided by the time taken, so stretching the catch over a longer time means a smaller force on the hands, and the catch does not hurt.

Option A is wrong because the fielder is removing momentum, not adding it. Option C is impossible; the mass of the ball cannot change. Option D confuses the issue, since the fielder reduces the rate at which the velocity changes rather than increasing it. The same idea explains a number of familiar safety measures: helmets and padded dashboards lengthen the time of impact, an athlete lands in a sand pit rather than on hard ground, and a person jumping down bends the knees on landing.