Two Identical Objects in Outer Space Have a Head-On Collision

Two identical objects in outer space have a head-on collision and stick together.If,before the collision,one had been moving at 2 m/s and the other at 1 m/s,their combined speed after the collision would be

A) 0) 5 m/s.
B) 0) 33 m/s.
C) 0) 67 m/s.
D) 1) 0 m/s.
E) none of these