An object of mass M is dropped near the surface of Earth such that the gravitational field provides a constant downward force on the object. Which of the following describes what happens to the center of mass of the object-Earth system as the object falls downward toward Earth? a. It moves toward the center of Earth. b. It moves toward the object. c. It does not move. d. The answer cannot be determined without knowing the mass of Earth and the distance between the object and Earth’s center.