Where does the aircraft supply oxygen for passengers come from?

The correct answer is that the aircraft supplies oxygen for passengers through chemical oxygen generators. These devices are designed to produce oxygen on demand and are typically activated in emergencies when cabin pressure drops or when supplemental oxygen is necessary.

Chemical oxygen generators contain a chemical solid that, when ignited, undergoes a reaction that releases breathable oxygen. This method is effective because it provides a reliable supply of oxygen without the need for heavy tanks or reliance on external sources. Each generator can supply enough oxygen for a designated number of passengers for a crucial period, ensuring safety during critical situations.

In contrast, ground-based oxygen tanks would not be feasible for in-flight emergencies since they are not part of the aircraft's onboard systems. Oxygen-rich tablets do not exist as a practical means of supplying oxygen in commercial aircraft. Electrolytic oxygen systems—while a plausible technology in certain contexts—are not typically used in commercial aviation for passenger situations, focusing primarily on military applications or specific spacecraft scenarios.