Answer:
A. The brightness of the bulb
Step-by-step explanation:
An electric current through a circuit turns the lights bulb on. the strength of the current created by the generator will be indicated by the brightness of the bulb because in a closed circuit, the bulb is the only object that is representing that, circuit is properly placed and when bulb lights up only when electrical energy is generated.
More electrical energy generated through the generator means the brighter the bulb glow.
Hence, the correct answer is "A. The brightness of the bulb".