What can be said about the velocity of the center of mass of the system of the two toy carts just before and after the collision?
A. The velocity of the center of mass before the collision is greater than the velocity of the center of mass after the collision.
B. The velocity of the center of mass before the collision is less than the velocity of the center of mass after the collision.
C. The velocity of the center of mass before the collision is the same as the velocity of the center of mass after the collision.
D. The velocity of the center of mass is always zero.