Assertion: The coefficient of performance or COP (sometimes CP or COP) of a heat pump, refrigerator or air conditioning system is a ratio of useful heating or cooling provided to work required.
Reason: Higher COPs equate to lower operating costs.
A) Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B) Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
C) Assertion is correct but Reason is incorrect
D) Both Assertion and Reason are incorrect

Hint: Coefficient of performance is the measure of how much energy is put to useful work. It is the ratio of heat extracted or the cooling provided from or to a body to the work done to transfer the heat. From this the amount of energy wasted can be measured which can lead to increase in operating costs. Higher COP means the work done is less therefore lowering the operating cost.

Complete step-by-step solution
Cop gives us the information as to how much energy is used in the process compared. It is essentially the ratio of useful heat or cooling work done to the work required. This can help us to find out the amount of energy wasted. This wasted energy is leaked as heat, friction, light, vibrations etc. Such leakages affect any machinery and damage it and will hence increase the cost of operation. Higher CoP means low losses which mean less wastage of energy and ultimately meaning less cost of operation.

Therefore, the correct answer is option A

Note A perfect refrigerator or a device is the one which transfers heat or provides cooling without doing any work. When the work done in such cases is zero, then the coefficient of performance is infinity and it has the lowest operating cost which cannot be achieved. For a refrigerator the COP will be zero if the cold body is at the temperature equal to absolute zero.