Answer:
B. Inelastic collision
Step-by-step explanation:
There are two types of collision:
- Elastic collision: in an elastic collision, both the total momentum of the objects and the total kinetic energy of the objects involved are conserved before and after the collision
- Inelastic collision: in an inelastic collision, the total momentum of the objects is conserved before and after the collision, while the total kinetic energy is not - in fact, some of the kinetic energy is converted into other forms of energy (such as thermal energy) due to the presence of frictional forces
In particular, a perfectly inelastic collision is an inelastic collision in which the two objects stick together after the collision: in such a situation, the amount of kinetic energy "lost" (=converted into other forms) is maximum.
In the situation described in the problem, the two skaters stick together after the collision, so this is an example of perfectly inelastic collision.