A body of mass m is rotated along a vertical circle of radius r such that velocity of the body at a point of vertical circle is equal to critical velocity at that point then:
A) maximum change in K.E. during one revolution is 2mgr
B) difference of maximum tension and minimum tension in the string is 6mg
C) the ratio of minimum tension to maximum tension in the string is 1:6
D) the ratio of minimum K.E. to maximum K.E. of the body is 1:5