A ball is thrown vertically upward from the surface of the earth. The ball rises to some maximum height and falls back toward the surface of the earth. Which one of the following statements concerning this situation is true if air resistance is neglected? a) As the ball rises, its acceleration vector points upward. b) The ball is a freely falling body for the duration of its flight. c) The acceleration of the ball is zero when the ball is at its highest point. d) The velocity and acceleration of the ball always point in the same direction.