What types of loads must be covered with a tarp?

C is correct because loads made of aggregate material or those that are likely to bounce or blow away can create significant safety hazards on the road. When transporting such loads, covering them with a tarp helps prevent spillage, which could lead to road hazards for other drivers and potential accidents. Furthermore, a tarp will minimize the risk of losing materials due to wind or tire movement, contributing to safer driving conditions.

In contrast, covering all types of loads regardless of their nature may not always be necessary; for instance, solid and stable loads that do not pose a risk of spillage may not require a tarp. Similarly, while loads sensitive to moisture might benefit from being covered, this is not the primary concern related to safety or regulation for all loads, making it a less encompassing choice. Heavy loads that are stable typically do not necessitate tarping unless they fit the more specific criteria identified in the correct answer.