The correct answer is b. The coefficient of performance (COP) is a measure of the efficiency of cooling appliances. Typically, the COP of a refrigeration cycle is much larger than 1, meaning that the appliance uses less energy to produce a unit of cooling than it would take to produce the same amount of heat. This efficiency is especially true of vapor compression refrigerators, which rely on the phase change of a refrigerant to achieve these results. The COP of a refrigeration cycle is also not dependent on the ambient temperature, as the efficiency comes from the physical process itself.