One end of mass less inextensible string of length l is fixed and other end is tied to a small ball of mass m. The ball is performing a circular motion in vertical plane. At the lowest position, speed of ball is √(20gl) Neglect any other forces on the ball except tension and gravitational force. Acceleration due to gravity is g.
At the highest position of ball, tangential acceleration of ball is -
(A) 0
(B) g
(C) 5 g
(D) 16 g