Which flag should be flown when an emergency arises and personnel need to be alerted?

The Oscar flag is the correct choice for signaling an emergency situation, as it is specifically used to indicate that there is a person overboard or that a vessel is in distress. The visual of the Oscar flag is recognized internationally and serves to quickly alert nearby vessels and personnel to the immediate need for assistance or heightened awareness.

This flag's symbolism emphasizes the importance of responding rapidly in emergencies, ensuring that other mariners are quickly informed and can take appropriate actions to assist if needed. The use of the Oscar flag in these contexts is crucial for maritime safety and effective communication, making it a standard practice in situations requiring urgent notification.