High-pressure starting air for large marine diesels is produced in two or more compressor stages rather than a single stage. What is the primary reason for staging the compression?

1. A. A single-stage compressor cannot achieve the required volumetric efficiency at high pressure
2. B. Staging allows oil mist to be separated between stages before it reaches the air receivers
3. ✓ Compressing air to high pressure in a single stage generates excessive heat, so intercoolers between stages remove that heatCorrect
4. D. A single-stage compressor would require a relief valve rated above the receiver design pressure