Dangerous goods transported on Ontario's roads and highways are identified:

The identification of dangerous goods transported on Ontario's roads and highways is primarily done through the use of specific markings and safety labels that indicate the classification of the goods. Each type of dangerous goods has a particular label that conveys crucial information regarding its handling and safe transport. This system enhances public safety and ensures that first responders are aware of the potential hazards in case of an incident.

The labeling system is designed not only to inform those involved in the transportation and handling of these goods but also to alert emergency personnel in the event of an accident. Therefore, using specific markings and safety labels is both a regulatory requirement and an essential practice for safety on the roads.

The other options provided do not accurately represent how dangerous goods are identified. Dangerous goods must always be clearly labeled to ensure proper handling and to mitigate risks associated with their transportation.