Which energy pathway allows sustained activity over a long period of time when oxygen is available?

The aerobic energy pathway is the correct choice for sustained activity over a long period of time when oxygen is available. This pathway uses oxygen to efficiently convert carbohydrates and fats into energy, making it ideal for prolonged activities such as long-distance running, cycling, or swimming. Aerobic metabolism produces ATP (adenosine triphosphate), which is the energy currency of cells, at a slower rate but provides a high yield of energy, allowing individuals to maintain their activity levels for extended durations.

In contrast, anaerobic pathways involve energy production without oxygen and are more suited for short bouts of high-intensity activities. These pathways can supply energy quickly but only for a limited time due to the accumulation of lactic acid and depletion of available glucose. The immediate energy pathway, such as the phosphagen system, provides a rapid burst of energy for short durations (like sprinting or weightlifting) but is not sustainable for long activities. Therefore, when considering sustained physical performance, the aerobic pathway is the preferred and necessary system for efficient, long-term energy production.