Explain why must a cooling system do work to transfer thermal energy?

Although internal energy will not spontaneously flow from a cold region to a hot region, it can be forced to do so by doing work on the system.Refrigerators and heat pumps are examples of heat engines which cause energy to be transferred from a cold area to a hot area. Usually this is done with the aid of a phase change, i.e., a refrigerant liquid is forced to evaporate and extract energy from the cold area. Then it is compressed and forced to condense in the hot area, dumping its heat of vaporization into the hot area. ARE YOU FROM K12?

Then the answer would be d then