Lav: The restroom facility onboard the A/C.

• A. Lavatory: The restroom facility onboard the A/C
• B. Lavage: The cabin water treatment system
• C. Lavish: A premium seating area
• D. Lava Stone Oven: In-flight cooking device

Answer: (A)

Lav uses in-flight shorthand for the lavatory, which is the restroom onboard the aircraft. This term is standard crew and maintenance vocabulary, so it best matches the prompt. The other options describe unrelated ideas: lavage is a washing process, not a cabin facility; lavish is an adjective meaning luxurious and not a specific area of the plane; and Lava Stone Oven sounds like a cooking device, which isn’t a recognized in-flight appliance.