Transfer hoses on vehicles must be?

Transfer hoses on vehicles must be listed to ensure they meet specific industry standards and safety regulations. "Listed" means that the hoses have been tested and approved by a recognized testing laboratory for safe use in transferring fuels or other liquids. This listing verifies that the hoses are suitable for the conditions under which they will be used, including factors such as pressure, temperature, and chemical compatibility. Using listed hoses is crucial for ensuring safety during fuel transfer operations, minimizing the risks of leaks, spills, or catastrophic failures.

Other options may provide important characteristics of transfer hoses, but they do not encompass the core requirement for compliance and safety. For instance, while flexibility is beneficial for maneuvering and connecting hoses, and steel can offer durability, neither aspect guarantees the hose has been tested for safety standards. Sealing is also important in preventing leaks, but it does not address the essential verification of the hose's overall safety and reliability as required by regulations. Thus, being listed is the key requirement that ensures safety and compliance.