Which change of state involves a release of energy?
a) boiling
c) condensation
d) melting
e) sublimation

Whenever a substance changes its state, the level of intermolecular interactions is changed. As substances transition from solid, to liquid to gas, the intermolecular transactions decrease, meaning that the energy of the molecules is greater in the case of gases than it is for solids. This energy is the reason they are able to overcome intermolecular interactions. Now, when we transition from a high energy state of matter, such as gas, to a state with lower energy, such as a liquid or solid, energy is released. In the cases of boiling, melting and sublimation (conversion of solid to gas), the substance is transitioning to a higher energy state.
Therefore, C. condensation releases energy as it is the transition from gas to liquid.