23. A student holds one end of a string in a fixed position. A ball of mass 0.2 kg attached to the other end of the string moves in a horizontal circle of radius 0.5 m with a constant speed of 5m/s. How much work is done on the ball by the string during each revolution?
(A) 0 J
(B) 0.5 J
(C) 1.0 J
(D) 2πJ
(E) 5πJ