Final answer:
The correct placard for carrying 500 pounds of explosives A and B is determined by transport regulation tables, which specify the required placards based on the class and quantity of the hazardous materials.
Step-by-step explanation:
According to the placard tables, if you're carrying 500 pounds of explosives A and B, the correct placard that should be used is determined by regulations that pertain to the transport of hazardous materials.
These regulations specify the types of placards required based on the quantity and class of the explosive material. In the United States, for example, the Department of Transportation provides a Hazardous Materials Table which includes specific placarding requirements for different hazardous materials, and guidance for these placards can be found in resources such as the Emergency Response Guidebook (ERG).
If both types of explosives fall under the same hazard class, a single placard representing that class and its division may be sufficient. However, if they belong to different classes or divisions with specific placarding requirements, then multiple placards or a DANGEROUS placard might be necessary. It's essential to comply with these regulations not only for legal reasons but also to ensure the safety of all involved in the transport and handling of such dangerous goods.