Regarding a reverse-osmosis type freshwater generator using multiple spiral-wound membrane modules, what statement is true?

Correct Answer: Option B — Modules may be piped in series to increase the freshwater purity.

Piping membrane modules in series forces the permeate from the first stage to pass through subsequent membranes. This multi-stage treatment significantly reduces the concentration of dissolved solids in the final product, thereby increasing the overall purity of the freshwater produced compared to a single-stage or parallel configuration.