A) One discharge phase begins before the previous discharge phase has been completed. This is the correct answer. The reason is that in a herringbone gear pump, the discharge phases of the two sets of gears overlap, resulting in a steadier discharge pressure compared to a simple spur gear pump. As one set of gears completes its discharge phase, the other set begins its discharge phase, creating a more continuous flow and a smoother discharge pressure. The other options are incorrect because they do not directly explain the reason for the steadier discharge pressure in a herringbone gear pump.