In an inelastic collision, the kinetic energy of the colliding objects is not conserved. This means that some of the initial kinetic energy is lost during the collision, often converted into other forms of energy such as sound or heat. Therefore, option III is incorrect, as the energy is not increased. However, linear momentum is always conserved in a collision, regardless of whether it is elastic or inelastic. This means that the total momentum before the collision is equal to the total momentum after the collision. Therefore, option IV is correct. Based on the explanations above, the correct answer is: II and IV only.