Where must the interphone station for ground personnel be located on a large turbojet-powered airplane?

The interphone station for ground personnel on a large turbojet-powered airplane needs to be located where it can be used effectively without drawing attention from inside the airplane. Option C emphasizes the importance of situating this communication device in a manner that maintains operational security and minimizes distractions or potential safety issues within the passenger or crew areas.

This placement allows ground personnel to communicate freely regarding ground operations and other pertinent information without interfering with flight operations or passenger comfort. Ensuring that the interphone station is not easily detectable from inside the aircraft helps maintain a controlled environment critical for safety and security during ground handling operations.

In contrast, places like the cockpit aren't suitable as they require clear and focused communication channels between the flight crew, while options that suggest visibility or detection are counterproductive to the objective of maintaining operational confidentiality and efficiency.