The ____ method injects a measured flow of pure oxygen into the air before it reaches the intake of the compressor.

The continuous-flow method is correct because it involves injecting a consistent and measured flow of pure oxygen into the air supply line before it reaches the compressor's intake. This approach ensures that the mixture of oxygen and ambient air is stable throughout the process, which is crucial for maintaining the desired nitrox mix with the appropriate oxygen percentage.

This method is widely used in dives requiring specific nitrox mixes, as it allows divers to accurately manage their breathing gas compositions. Continuous flow provides a constant supply of oxygen that can be easily adjusted as needed, allowing for flexibility and precision in preparing nitrox blends.

The other methods listed do not offer the same level of control or consistency that the continuous-flow method provides, which is essential for blending gases effectively and safely.