Mechanics

​Q6. One end of a light spring of natural length d and spring constant k (= mg/d) is fixed on a rigid support and the other end is fixed to a smooth ring of mass m which can slide without friction on a vertical rod fixed at a distance d from the support. Initially, the spring makes an angle of 37° with the horizontal as shown in the figure.The system is released from rest. The speed of the ring at the same angle subtended downward will be 

        (A) $\sqrt{2\mathrm{gd}}$                                                     (B) $\sqrt{3\mathrm{gd}}$

        (C) $\sqrt{4\mathrm{gd}}$                                                      (D) $\sqrt{\mathrm{gd}/ 2}$