During repairs it is necessary to replace an existing vessel bulkhead. Drawings indicate it is a "B" class bulkhead. This indicates which of the following?

Correct Answer: Option B — "B" class bulkheads must not allow flame passage for 30 minutes when subjected to a fire test.

Per 46 CFR 72.05, 'B' class bulkheads are constructed of approved non-combustible materials. They must be capable of preventing the passage of flame for at least 30 minutes during a standard fire test, providing essential fire containment within accommodation and service spaces to protect escape routes.