If your vessel is to carry ten portable foam fire extinguishers, you must maintain a supply of at least __________.

Correct Answer: Option C — five spare charges

Per 46 CFR, vessels are required to maintain a specific reserve of extinguishing agents. For portable foam extinguishers, the regulations mandate that at least 50% of the total number of extinguishers carried must have a spare charge available, ensuring the vessel remains prepared for immediate fire suppression.