What should a controller do if an aircraft is approaching without a strip?

In situations where an aircraft approaches without a strip, the controller’s priority should be to ensure safety and maintain situational awareness. Engaging with the aircraft directly allows the controller to establish communication, ascertain the aircraft's position, intentions, and any potential emergencies it might be facing. This proactive approach is essential for maintaining effective air traffic management.

By contacting the aircraft, the controller can gather vital information that may not be visible on a strip, such as the aircraft's altitude, speed, and flight plan status. This interaction aids in understanding the situation better and allows the controller to provide appropriate instructions or assistance, ensuring the safety of both the aircraft in question and others in the vicinity.

The other choices present less effective responses. Ignoring the aircraft would create a dangerous gap in communication and information flow, while advising the aircraft to hold without understanding its circumstances could lead to mismanagement of air traffic or place the aircraft in a precarious situation. Posting an emergency strip may be necessary if the aircraft is in distress, but the immediate need should be to establish communication to determine the best course of action based on the aircraft's situation.