What should the status of a lavatory smoke detector be before a flight?

The lavatory smoke detector should be in a normal operating condition before a flight, which is indicated by a green light signaling that it is functional and properly monitoring for smoke. A green status means that the smoke detector has passed its pre-flight checks and is ready to detect any smoke that may occur during the flight, ensuring the safety of passengers and crew.

Investigating the other options provides context: if the smoke detector is non-functional, indicated by a non-green status or a red light, it would not fulfill its safety purpose. Having the smoke detector off or without any light indication would also mean it is not actively monitoring the lavatory. Therefore, ensuring that the smoke detector shows a green light before departure crucially supports the safety protocols on board.