In a marine diesel starting-air system, starting-air receivers are typically sized to provide how many consecutive starts for a reversible main engine before recharging is required?

Why D is correct

DOE-HDBK-1018 Vol.1 §1-5 states that receivers commonly hold enough air for twelve consecutive starts for a reversible main engine before recharging is required. This capacity ensures the engine can be started and maneuvered without interruption to recharge the system.