Final answer:
The power train of placarded vehicles must have a fire extinguisher with a UL rating of 10 B:C or more.
Step-by-step explanation:
The power train of placarded vehicles must have a fire extinguisher with a UL rating of 10 B:C or more. The UL rating is a classification system that indicates the fire suppression capability of an extinguisher.
The rating consists of two parts, the letter which represents the type of fire the extinguisher can effectively put out, and the number which indicates the extinguishing power in relation to the square footage of the fire source.