What is typically marked on a class nine placard?

Class nine placards are used for materials that present miscellaneous hazards during transportation. This category of hazardous materials does not fall under any other specific class, such as explosive, flammable, or corrosive materials, but still poses a risk in terms of safety and handling. The "miscellaneous hazards" classification can include a variety of items, such as dry ice, environmentally hazardous substances, or elevated-temperature materials.

In contrast, the other choices refer to specific classes of hazardous materials. Infectious substances, toxic chemicals, and corrosive materials all belong to their own distinct classes (Class six, Class two or three, and Class eight, respectively) and are represented by their specific placards. Therefore, the designation of a class nine placard specifically indicates that the substance does not conform to the defined categories of the other classes, thus solidifying its place in the miscellaneous hazards classification.