A stone of mass 1 kg tied to a light inextensible string of length (10/3) m is whirling in a circular path in a vertical plane. If the ratio of the maximum tension in the string to the minimum tension is 4 and if g is taken to be 10 m/s2 , the speed of the stone at the highest point of the circle is
(A) 5 √2 m/s
(B) 20 m/s
(C) 10 m/s
(D) 10 √3 m/s
