In an RV, each seating location must have a seat belt or be what?

The correct choice emphasizes that any seating location in an RV without a seat belt must be clearly marked to indicate that it cannot be used while the vehicle is in motion. This is important for ensuring passenger safety and compliance with regulations. By marking these seats, it informs passengers that those particular positions are not safe for occupancy when the RV is moving, thereby reducing the risk of injury during travel. Clear signage serves as a reminder and promotes responsible behavior among occupants, ensuring everyone understands the limitations of specific seating arrangements within the vehicle.

The other options might address aspects of safety or seating comfort but do not meet the specific regulatory requirement that mandates a clear indication of unusable seating while in motion.