True or False: Placards that contain the DOT Class 6 may represent an infectious substance.

The statement is true. Placards that display the DOT Class 6 label indeed represent hazardous materials, specifically those that include infectious substances. According to the Department of Transportation (DOT) regulations, Class 6 is designated for toxic substances and infectious substances.

Infectious substances are categorized under Division 6.2 within this class and are intended to denote materials that can cause disease in humans or animals. Therefore, when a placard indicates DOT Class 6, it can be associated with various materials that are capable of being infectious.

The other choices do not adequately capture the relationship between the placards and infectious substances, as they either restrict the situation to rare cases, suggest limitations that are not in accordance with DOT classification, or imply uncertainty where the classification is clear.