Final answer:
Branch connections off the main gas supply line in a recreational vehicle should be made with rigid piping to ensure safety and reliability. Flexible hoses and compression fittings are less desirable due to the potential for leaks and insufficient durability.
Step-by-step explanation:
On a recreational vehicle, all branch connections off the main gas supply line should be made using rigid piping. This is critical for ensuring the safety and reliability of the gas supply system within the vehicle. Flexible hoses may not provide the necessary durability or security, especially when the vehicle is in motion, leading to potential hazards. Compression fittings, while useful in some scenarios, may not offer the same level of security and leak prevention as rigid connections. The specified method aligns with safety protocols and the guidelines set forth by regulatory bodies governing RV construction and maintenance.