Which equipment is not necessary for Visual Flight Rules (VFR)?

In the context of Visual Flight Rules (VFR), certain equipment is deemed essential for safe operation while other items, although helpful, are not strictly necessary for VFR compliance. A Mode C transponder, which transmits altitude information to air traffic control, is specifically required only in certain airspace classifications, such as Class B and Class C airspace, or above 10,000 feet in Class E airspace. However, for VFR operations in less controlled airspaces or below these altitudes, having a Mode C transponder is not a necessity.

On the other hand, the other items listed are critical for VFR flying. A headset is important for communication with air traffic control and coordination with other pilots. The fuselage is the main body of the aircraft, which is essential for the aircraft's structural integrity and safety. An altimeter is critical for proper altitude awareness and navigation during flight. Therefore, while the Mode C transponder has its relevance, it is not universally required for all VFR operations, making it the correct answer in this scenario.