The correct answer is B. Watt.
A watt (W) is a unit of power in the International System of Units (SI). It is defined as one joule of energy per second. Power is the rate at which energy is transferred or converted. In electrical circuits, power is the rate at which electrical energy is converted into other forms of energy, such as heat, light, or mechanical work.
A bolt is a unit of electrical potential difference. It is equal to the potential difference that would cause a current of one ampere to flow through a resistance of one ohm.
A kilowatt hour (kWh) is a unit of energy. It is equal to one thousand watt hours, or one thousand joules per second multiplied by one hour.
An ampere (A) is a unit of electric current. It is defined as the current that flows through a conductor when a potential difference of one volt is applied across it, and the resistance of the conductor is one ohm.
In conclusion, the unit of electrical power is the watt.