Explanation: NMEA 2000 networks are based on the Controller Area Network (CAN) bus standard, which has specific cabling requirements to ensure reliable high-speed data communication. The NMEA 2000 specification limits the length of a drop cable connecting a single device to the main backbone to a maximum of 6 meters (approximately 20 feet). This limitation is crucial for maintaining signal integrity on the network. Longer drop cables can introduce excessive capacitance and inductance, leading to signal reflections and attenuation. These effects degrade the high-speed data signals, causing intermittent communication errors, device malfunctions, or even complete network failure. Adhering to the 6-meter limit prevents these issues, ensuring stable and reliable network operation. The other lengths would exceed this critical specification.