What is statement is true concerning the term "isochronous" as it applies to prime mover speed control governors?

Correct Answer: Option C — Isochronous governors are able to maintain constant prime mover speed regardless of load by employing temporary speed droop.

Isochronous governors maintain a constant prime mover speed regardless of load variations. They achieve this by utilizing temporary speed droop, which allows the governor to compensate for load changes without a permanent offset in the steady-state speed. This is critical for maintaining precise frequency control in shipboard electrical power generation.