What is the purpose of the "kill switch" on a boat?

The correct choice highlights the critical safety function of the "kill switch" on a boat. The main purpose of the kill switch is to automatically shut down the engine if the operator unexpectedly leaves their seat or is thrown from the boat. This mechanism is vital in preventing the boat from operating unattended, which could lead to dangerous scenarios such as collisions or the boat continuing to move in circles if the operator falls overboard.

Understanding this safety feature emphasizes the importance of proactive measures while boating, as it helps protect the operator and passengers from potential accidents resulting from an uncontrolled vessel. The other options, while they address aspects of boating safety or navigation, do not accurately describe the primary function of the kill switch. For instance, signaling for help, controlling speed, or alerting nearby vessels involves different tools and practices that do not align with the essential purpose of the kill switch.