Regarding the study of heat and energy, analyze the following statements:
I- The unit of heat is Joule (J).
II- The specific heat is a characteristic of each substance that indicates the amount of heat that must be given or taken from each unit of mass to change its temperature by one unit.
III- The capacity heat is proportional to the mass of the body and indicates the amount of heat that must be given or taken from a body to change the temperature of the entire body by one unit.
IV- The conservation of energy principle states that when bodies at different temperatures are put in contact, they will exchange heat until reaching thermal equilibrium, and the heat gained by the cold bodies must be equal to the heat lost by the hot bodies.

a) Only statements I and II are correct.
b) Only statements II and III are correct.
c) Only statements III and IV are correct.
d) All statements are correct.