Answer
d) is correct.
Work Step by Step
There is no external force, so the momentum is conserved. Therefore, the total momentum before the collision and after the collision has to be the same: $$p_{01}+p_{02}=p_{f1}+p_{f2}$$
So a) and c) are eliminated.
Because the collision is elastic, kinetic energies are conserved, too. $$\sum KE_0=\sum KE_f$$
Therefore, d) is correct.
