A ball of mass m is attached to one end of a light rod of length $l$, other end of which is hinged . What minimum velocity 'v' should be imparted to the ball downwards so that it can complete the circle

Question

$$(a)\;\sqrt {gl} \quad (b)\;\sqrt {5gl} \quad (c)\;\sqrt {3gl} \quad (d)\; \sqrt {2gl}$$