The high-level overfill tank alarm, installed in the on-board monitoring system, must __________.

Correct Answer: Option B — be both audible and visual

Under 46 CFR 39.2007, high-level and overfill tank alarms must provide both an audible and a visual signal at the cargo control station. This dual-signaling requirement ensures immediate watchstander awareness to prevent accidental oil spills during cargo transfer operations.