Final answer:
The scenario describing a perfectly inelastic collision is when two rams collide and their horns get locked, moving together afterwards.
Step-by-step explanation:
The scenario that describes a completely inelastic collision is d) Two rams start to fight by running toward each other and colliding with their heads. As a result, their horns get locked as they continue to fight. In a completely inelastic collision, the objects involved stick together after their collision, moving with a common velocity. This situation is evident in the scenario where the rams' horns get locked together during the fight, illustrating a perfectly inelastic collision.
A completely inelastic collision is one where the two objects stick together after the collision and move with a common velocity. In the given scenarios, the only example of a completely inelastic collision is scenario d. When two rams collide with their heads, their horns get locked and they continue to fight with a common velocity.