What must the source do continuously as you track it?

The correct choice highlights the importance of continuous communication and tracking in various operational environments. When tracking a source, whether it be a vessel, an object, or a signal, it is crucial for the source to emit signals regularly. This consistent emission of signals allows for accurate tracking, ensuring that the positioning and movement can be monitored effectively. These signals could be in the form of radar pings, radio transmissions, or other identifiable markers that enable maintainability of situational awareness.

Without these emitted signals, tracking becomes significantly more challenging, as it would require other methods to verify the source's location and movement, which may not be as reliable in dynamic conditions. Therefore, continuous emission of signals is essential for effective tracking in maritime operations.