Which One of the Following Statements Concerning Center of Mass

Multiple Choice

Which one of the following statements concerning center of mass is true?

A) All of an object's mass is located at its center of mass.
B) The center of mass of an object must be located within the object.
C) The center of mass of a system of objects cannot change even if there are forces acting on the objects.
D) The velocity of the center of mass of a system of objects is greatly affected by a collision of objects within the system.
E) The velocity of the center of mass of a system of objects is constant when the sum of the external forces acting on the system is zero.