Which example involves a phase change in which heat energy is released by the substance? freezing ice cream cooking a pot of soup melting ice under sunlight watching frost disappear into air

Cooking soup does not induce a phase change in the water as it is still water. Melting is an endothermic reaction in that it draws in heat which also applies to the frost disappearing. Freezing is an exothermic reaction in that it gives off energy in order to make what being frozen colder which satisfies answer A.