Two spheres A and B moving in opposite directions have velocities of 10ms^-1 and 20ms^-1. The two spheres collide with each other elastically. If A continues to move in the same direction at 4 m$s^{-1}$, the velocity of sphere B just after the collision is

• A

  34 m/s in the same direction of A

• B

  34 m/s in the opposite direction of A

• C

  26 m/s in the same direction of A

• D

  26 m/s in the opposite direction of A