What component of a reverse-osmosis freshwater generator could be isolated and replaced with the unit remaining in service?

Correct Answer: Option B — A parallel-connected membrane module.

Parallel-connected membrane modules allow individual isolation via valves while the remaining modules continue to process feedwater. This design ensures operational continuity during maintenance or replacement of a fouled module, adhering to standard marine auxiliary machinery design practices for maintaining essential shipboard freshwater production without requiring a full system shutdown.