Q. A boy sitting in a rail road car throws a ball straight up into the air. The ball will fall back into his hands when the rail road car is

• (A) moving at constant velocity
• (B) accelerating forward while going around a curve of radius equal to the maximum height attained by the ball
• (C) accelerating forwardA block A is dropped down a smooth inclined plane, while another identical block B is released for free fall from the same height
• (D) decelerating