What is a common requirement for cargo being transported in combination vehicles?

The requirement that cargo must not exceed weight limits and be properly secured is crucial when transporting cargo in combination vehicles. Overloading a vehicle can lead to instability, increased stopping distances, and higher risks of accidents, particularly when navigating turns or sudden stops. Moreover, securing the cargo is essential to prevent it from shifting during transport, which can create hazards for the driver and other road users. Safe transport practices help ensure that both the vehicle and the load are within legal and safety parameters, thus promoting overall road safety.

While securing cargo with ropes and ensuring it is identifiable by labeling can be useful, they are not universally mandated for all scenarios or types of cargo in combination vehicles, making option C the most comprehensive and critical requirement. Additionally, not all cargo needs to be covered, as some may be weather-resistant or not sensitive to environmental conditions, making the other choices less broadly applicable.