Explanation: EPIRB (Emergency Position Indicating Radio Beacon) batteries are critical for maritime safety and are subject to specific regulations to ensure they function when needed most. The correct answer, **B),** reflects these requirements: * **After emergency use:** Once activated, an EPIRB's battery is designed to operate for a minimum duration (e.g., 48 hours for Class A/B) and should be replaced regardless of the duration of activation. * **Within the month and year replacement date printed on the EPIRB:** Manufacturers provide an expiration date for the sealed primary batteries, typically 5 years, ensuring the battery retains sufficient charge and capacity over time. This printed date is a regulatory requirement to guarantee reliability. **Why other options are incorrect:** * **A) "After emergency use; after battery life expires"**: While similar, "after battery life expires" is less precise than the specific "month and year replacement date printed on the EPIRB," which is the actionable regulatory trigger. * **C) "Every 12 months when not used"**: This is too frequent; EPIRB batteries have a multi-year lifespan. * **D) "Whenever voltage drops to less than 20% of full charge"**: EPIRBs are sealed units, and users do not typically monitor their internal voltage. Replacement is based on the printed expiration date or after use, not on real-time voltage monitoring.