Heat is a form of energy that gets transferred from one medium or object to another medium/object. Suppose if we a colder body and a hotter body and if it brought in contact, the heat gets transferred from the hotter body to colder body until the system of hotter & colder attains equilibrium.When two bodies at different temperatures are placed in thermal contact with each other, heat flows from the body at a higher temperature until they both acquire the same temperature. Assuming that there is no loss of heat to the surroundings, then The heat lost by the hotter body will be equal to the heat gained by the colder body.option D is correct