Which application device does not require physical modifications to the fuselage?

The choice regarding self-contained tank-and-boom systems is correct because these systems are designed to be independent units that integrate both the tank and the boom into a singular module that can be attached to the aircraft without the need for significant modifications to the fuselage. This modular nature simplifies installation and allows for greater versatility since the system can be installed or removed as needed.

On the other hand, centrifugal spreaders and spray booms typically require adaptations to the aircraft's fuselage. For instance, spray booms often need to be mounted in a way that involves structural changes to adequately support them and ensure safe and proper operation, while centrifugal spreaders might also necessitate alterations or reinforcements to the fuselage to accommodate their weight and function effectively. Therefore, self-contained systems provide a practical solution for aerial application by minimizing the need for physical modifications.