What type of covering is required for loose materials on a vehicle?

The correct choice highlights that canvas or tarps are the preferred coverings for loose materials on a vehicle. This type of material is durable, flexible, and able to securely cover and contain the loose items while being resistant to various weather conditions. Tarps, for example, can be easily tied down, ensuring that the loose materials do not get dislodged during transport, which is crucial for safety regulations as well as road safety.

When considering the other options, while cardboard may provide a temporary solution, it is not as robust or wind-resistant, making it less reliable for covering loose materials. Plastic sheets might lack the sturdiness and tiedown capacity needed to effectively secure materials during transit. Metal sheeting, although effective in some contexts, is generally too heavy and not practical for loose loads, making it an impractical choice for this purpose. Thus, the choice of canvas or tarps aligns best with safety and practicality in transporting loose materials.