Why does the rate of air usage increase with depth?

The rate of air usage increases with depth primarily due to the greater density of air. As a diver descends, the surrounding water pressure increases, which also compresses the air in their tank and increases the density of the air being breathed. The body requires more work to inhale more densely packed air, leading to higher gas consumption.

While the other options mention factors such as pressure and temperature, they do not accurately align with the physiological and physical changes that occur with depth. Increased pressure does not decrease air usage; rather, it is the opposite. Temperature can affect gas behavior but is not the main factor influencing increased air consumption at greater depths. Equipment malfunction, while a concern, does not typically relate directly to the increase in air consumption as a result of depth. Understanding the relationship between buoyancy, pressure, and gas density is crucial for advanced diving practices.