The correct answer is D) tested monthly. The Emergency Position Indicating Radio Beacon (EPIRB) is a critical safety device that must be tested regularly to ensure it is functioning properly and will activate in an emergency. According to U.S. Coast Guard regulations, the EPIRB must be tested monthly to confirm its readiness. This regular testing requirement ensures the EPIRB will be able to alert search and rescue authorities if the vessel is in distress. The other answer choices are incorrect because they do not align with the Coast Guard's testing requirements. The EPIRB should not be secured inside the wheelhouse or the emergency locker, as it needs to be accessible and able to float free in an emergency. Annual testing is also insufficient, as monthly checks are mandated to maintain the EPIRB's operational readiness.