How is a casualty on board called away with bells?

The process of calling away a casualty on board a vessel involves the use of the ship's bells to alert the crew. The correct answer specifies that there is a rapid ringing followed by single strikes. This method is standard practice to communicate the nature of the situation and the urgency involved.

When a rapid ringing occurs, it signals that immediate attention is required. The multiple rapid rings indicate that there is a serious incident unfolding, prompting crew members to respond quickly. Following this frantic ringing with single strikes serves to provide additional clarity about the specific situation, often denoting the number of casualties, such as one strike for one individual in need of assistance.

The other choices do not align with established maritime communication protocols. Soft ringing only once would not effectively convey the urgency of a casualty situation. Continuous ringing until help arrives doesn’t specify any follow-up signals or clear guidance on how many individuals require assistance. Ringing the bell only when medical personnel arrive fails to initiate the immediate response that is critical in emergencies. Hence, the correct process of calling away a casualty combines both the rapid ringing and the subsequent strikes to effectively communicate urgency and the specific nature of the situation to the crew.