Which statement describes a function of the oxygen mask?

• A. Powers life support systems
• B. Filters cabin air
• C. Provides breathing gas on demand at a pressure schedule dependent upon altitude
• D. Helps regulate cabin temperature

Answer: (C)

The main idea is how an oxygen mask delivers breathable gas when you need it, and how that supply adjusts with altitude. The mask isn’t there to power systems, filter cabin air, or regulate temperature. Its job is to provide breathing gas on demand through a regulator that responds to your inhalation and increases supply pressure as altitude rises. This pressure schedule ensures you get enough oxygen even as ambient pressure drops. That’s why the statement describing oxygen on-demand gas delivery with altitude-dependent pressure best fits the function of the oxygen mask.