Under what condition will both the red and green lights be ON?

In understanding the functioning of electrical circuits, particularly those involving indicator lights, it's important to consider how circuits are designed to operate regarding the states of switches and the control inputs.

When we're told that both the red and green lights cannot be ON simultaneously—choosing the option indicating that it will never happen—implies that these lights are designed to indicate mutually exclusive conditions or states within the circuit. Often, one light turning ON typically indicates that the other must be OFF, which can be a common design in safety or operational protocols, such as in traffic lights or other signaling applications.

In circuits, control systems are usually configured so that either one condition is true or the other, but not both at the same time. This prevents confusing signals and ensures clear communication of the current state to users.

Therefore, the conclusion that both lights being ON will never occur highlights an understanding of how electrical control systems often make use of logic designs to ensure clear, distinct indications.