Final answer:
The number of oxygen masks in each lavatory varies depending on the size of the aircraft.
Step-by-step explanation:
The correct answer is (D) The number of oxygen masks in each lavatory varies depending on the size of the aircraft. The number of oxygen masks in each lavatory is determined by the regulations set by aviation authorities and varies depending on the size and capacity of the aircraft. Larger aircraft usually have more oxygen masks in each lavatory to accommodate more passengers.