If a casualty is trapped in a collapsed building and cannot be moved, what should be transmitted at line 4?

The correct answer relates to the specific situation of a casualty being trapped in a collapsed building where immediate extraction may not be possible. In this scenario, it is vital to communicate critical information about the casualty's condition and the necessity for specialized resources.

Transmitting the need for extraction equipment is crucial because it alerts responding teams to the complexity of the situation. The responders need to be prepared with the necessary tools and equipment, such as hydraulic rescue tools, to safely free the trapped individual without further risking their safety or exacerbating any injuries they may have sustained. This type of information ensures that rescue operations can be efficiently organized, with the right personnel and equipment on hand when they arrive at the scene.

The other choices, while potentially relevant, do not prioritize the immediate need for the specialized equipment required to address the unique challenges of a building collapse. Understanding the specific needs of the situation ensures an appropriate and timely response to save lives.