Two smooth spheres P and Q collide elastically on a horizontal frictionless table. Sphere P of mass m moves with speed u towards stationary sphere Q of mass M. Which one of the following statements is always true about the directions of their velocities just after collision?
a) They are mutually perpendicular only when m≫M.
b) They are mutually perpendicular only when m=M.
c) They are always mutually perpendicular irrespective of the masses.
d) They are always parallel to each other.