The correct answer is C) have a duplicate set of plans permanently stored outside the deck house. The requirement for a vessel's fire control plan to have a duplicate set of plans permanently stored outside the deck house is specified in U.S. Coast Guard regulations. This is to ensure that the fire control plan is accessible in the event of an emergency, even if the primary location of the plan inside the deck house is inaccessible. The other answer choices are incorrect because: A) the fire control plan does not need to provide information about crew members' staterooms, B) the plan does not need to be posted in every crew space, and D) the plan does not need to be written in Spanish and English (unless the vessel operates in a jurisdiction that requires it).