Final answer:
The correct answer is d) DC power source, electrode -, referring to a direct current power source where the electrode is negative and there is a unidirectional flow of electric charge.
Step-by-step explanation:
Reverse polarity typically refers to a situation in welding where the electrode is connected to the negative terminal of a power source. In the context of the question, the correct answer is d) DC power source, electrode -. This means that we are using a direct current (DC) power source, where the flow of the electric charge is only in one direction, from the negative terminal to the positive terminal of the power source. Many devices that we use in daily life, such as computers, cell phones, and cars, operate on DC. The source of this DC current can be a battery, which provides a constant potential, or a transformer that converts alternating current (AC) from a wall socket to DC for device charging.