Two Identical Carts Travel at 1 M/s on a Common

Multiple Choice

Two identical carts travel at 1 m/s on a common surface. They collide head-on and are reported to rebound, each with a speed of 2 m/s. Then:

A) momentum was not conserved, therefore the report must be false
B) if some other form of energy were changed to kinetic during the collision, the report could be true
C) if the collision were elastic, the report could be true
D) if the surface were inclined, the report could be true
E) if the duration of the collision were short enough, the report could be true