Context: The passage below describes an experiment. Read the passage and then follow the instructions below.

Gina built an electric circuit: she used wires to connect a battery to a light bulb, the light bulb to a small piece of copper, and the copper back to the battery. When the circuit was complete, the light turned on. Gina observed the brightness of the light for five seconds. She then replaced the copper with a piece of iron of equal size and noted whether the light became brighter or dimmer. Gina built three more of the same type of circuit. She repeated the tests with each circuit. Gina recorded whether the circuits produced brighter light when the circuit included copper or when the circuit included iron.
Figure: a circuit with a battery, a light bulb, and a piece of copper.
Identify the question that Gina's experiment can best answer.
A. Can light bulbs stay lit longer when circuits include copper or when circuits include iron?
B. Do circuits that include iron produce dimmer light than circuits that include copper?
Choose the right answer from the options and respond with its letter.

B