Final answer:
The correct placard for a load containing materials from more than one hazard class is the "Dangerous" placard.
Step-by-step explanation:
The placard used for a load that contains materials from more than one hazard class is the "Dangerous" placard. This placard is a signal that multiple hazardous materials exist in the shipment and precautions should be taken when handling. Placarding is crucial for ensuring the safety of those handling the shipment and for emergency responders in case of an accident. Under the regulations by the Department of Transportation (DOT), when a shipment includes multiple classes of hazardous materials, the "Dangerous" placard serves to communicate these multiple risks effectively.