In which scenario is a placard displaying the number "1203" applicable?

The number "1203" on a placard is associated specifically with gasoline, which is classified as a flammable liquid. The use of this placard is mandated for hazardous material transportation to communicate essential safety information regarding the material being transported. This placarding serves to notify first responders and others about the presence of gasoline, helping to ensure proper precautions are taken in the event of an accident or spill.

In the context of the other options, diesel fuel, propane, and kerosene each have their own specific UN (United Nations) identification numbers and corresponding placards. For example, diesel fuel is designated with the number "1202," propane is identified by "1978," and kerosene by "1223." This differentiation is crucial for safety and compliance reasons, making the recognition of the correct placard number vital for anyone involved in the handling or transportation of hazardous materials.