20. The figure shows a rough semicircular track whose ends are at a vertical height h . A block placed at point P at one end of the track is released from rest and slides past the bottom of the track. Which of the following is true of the height to which the block rises on the other side of the track?
(A) It is equal to h/4
(B) It is equal to h/2
(C) It is equal to h
(D) It is between zero and h ; the exact height depends on how
much energy is lost to friction.