One of the methods used to reduce energy use is:
a. energy efficiency
c. energy conservation
b. energy reservation
d. energy holding

One of the methods that best describe the reduction of energy is energy conservation. It is the usage of less energy service that it usually utilizes. An example is using bike for transportation instead of a car to save fuel. The answer is letter B. It is not energy efficiency because it represents how efficient a substance can convert work at 100%. It is not reservation because there is no term for it. It is not energy holding because it defines the how much energy the body can hold.

This is what a calorimeter is used for simpler ex, to measure calories in food.