Which Is the Best Description of a Watt

Which is the best description of a watt?

A) The amount of power consumed when a one-volt dc power source causes a current of one amp to flow in a circuit.
B) The amount of power consumed when a one-volt ac power source causes a current of one amp to flow in a circuit.
C) The amount of voltage consumed when a one-volt dc source causes a resistance of one ohm in a circuit.
D) The amount of current consumed when a one-volt ac source causes a current of one amp to flow in a circuit.