A particle is dropped from a height $h .$ Another particle was what initially at a horizontal distance $d$ from the first, is simultaneously projected with a horizontal velocity $u$ and two particles just collide on the ground. The three quantities $h, d$ and $u$ are related to
(a) $d^{2}=\frac{u^{2} h}{2 g}$
(b) $d^{2}=\frac{2 u^{2} h}{g}$
(c) $d=h$
(d) $g d^{2}=u^{2} h$