A bead of mass slides without friction on the wall of a vertical circular hoop of radius as shown in figure. The bead moves under the combined action of gravity and a massless spring attached to the bottom of the hoop. The equilibrium length of the spring is . If the bead is released from the top of the hoop with (negligible) zero initial speed, the velocity of the bead, when the length of spring becomes , would be (spring constant is , is acceleration due to gravity):

- A
- B
- C
- D
