A placard cannot be placed closer than ___ from any other markings.

The correct answer indicates that a placard must not be placed closer than 3 inches from any other markings. This requirement is in place to ensure that the placard is clearly visible and that its information is not mistakenly interpreted due to proximity to other markings or labels. Clear visibility of placards is crucial in hazmat transport since these signs communicate essential information regarding the type of hazardous material being transported and the necessary precautions that should be taken. Maintaining a specific distance also helps transport personnel, emergency responders, and the general public recognize and understand the potential risks associated with a particular shipment without confusion.