The correct answer is C. an integrating instrument.
An indicating instrument is a device that shows the value of a quantity, such as the voltage or current in an electrical circuit. A recording instrument is a device that records the value of a quantity over time. An integrating instrument is a device that integrates the value of a quantity over time, giving the total amount of the quantity that has occurred over a period of time.
A household energy meter is an integrating instrument because it measures the total amount of energy that has been used by a household over a period of time. This information is used to calculate the household’s energy bill.
An indicating instrument would not be able to provide the information that is needed to calculate a household’s energy bill. A recording instrument would be able to provide this information, but it would not be able to provide the total amount of energy that has been used by the household over a period of time.