Which of the following freshwater generators has an operating principle that requires it to run under a substantially positive pressure?

Correct Answer: Option C — Reverse-osmosis unit

Reverse-osmosis units must operate at high positive pressures, often exceeding 800 psi, to overcome the osmotic pressure of seawater. This mechanical pressure is the fundamental driving force for the separation process, distinguishing it from vacuum-based evaporators that rely on reduced pressure to lower the boiling point of the feedwater.