A ball is thrown vertically downwards from a height of 20 m with an initial velocity v02. It collides with the ground, loses 50 percent of its energy in collision and rebounds to the same height. The initial velocity v0 is (Take g = 10 ms-2)
(A) 10 ms-1
(B) 14 ms-1
(C) 20 ms-1
(D) 28 ms-1