Answer : (D) " in the opposite direction of "
Explanation :
It is given that when object A collides with object B and bounces back. This shows that the collision is elastic. There are two conditions for elastic collision :
(1) The momentum remains conserved
(2) Kinetic energy is conserved.
We know that momentum is defined as the product of mass and velocity. After bouncing back, the direction of velocity gets changed. So, the final momentum is in the opposite direction of its initial momentum.
So, the correct option is (D).