The correct answer is option 3, electric energy.
A kilowatt-hour (kWh) is a unit of measurement used to quantify the amount of electrical energy consumed or produced over a period of time. It is derived from the product of power (measured in kilowatts) and time (measured in hours).
Option 1, potential difference, is not correct because potential difference is measured in volts, not kilowatt-hours.
Option 2, electric power, is also not correct because electric power is measured in kilowatts, but it does not encompass the aspect of time. Electric power is the rate at which energy is transferred or used.
Option 4, electric potential, is not correct because electric potential is measured in volts, not kilowatt-hours.
Therefore, option 3, electric energy, is the correct unit of measurement for a kilowatt-hour. It represents the amount of electrical energy consumed or produced over a period of time.