Final answer:
The power unit of a placarded vehicle must have a fire extinguisher with a UL rating of 10 B:C or more.
Step-by-step explanation:
In the transportation industry, placarded vehicles must adhere to certain safety regulations. One of these regulations states that the power unit of a placarded vehicle must have a fire extinguisher with a UL rating of at least 10 B:C or higher.
The UL rating is a classification system used for fire extinguishers. The rating consists of two parts - the letter rating (A, B, or C) which indicates the types of fires the extinguisher can be used on, and the numerical rating which indicates the extinguishing power of the extinguisher.
In this case, the UL rating of 10 B:C means that the fire extinguisher is capable of extinguishing fires of class B and C, such as fires involving flammable liquids (class B) and electrical fires (class C).