A particle of mass m and velocity V collides obliquely elastically with a stationary particle of mass 'm'. The angle between the velocity vectors of the two particles after the collision is

Question

\[\begin {array} {1 1} (a)\;45^{\circ} & \quad (b)\;30^{\circ} \\ (c)\;90^{\circ} & \quad  (d)\;None\;of\;these \end {array}\]