Final Answer:
Class B, in the context of flammable and combustible materials, specifically designates that flammable materials, as defined in this class, can burn at normal temperatures without requiring additional heating. So, the correct answer is A) Defines materials that burn at normal temperatures.
Step-by-step explanation:
Class B Definition: Class B is associated with flammable and combustible materials, providing a framework for understanding their fire characteristics.
Flammable Materials: The choice A accurately describes the definition of flammable materials within Class B, indicating that these materials can ignite and burn at normal temperatures without the need for external heating.
Contrast with Combustible: Combustible materials, on the other hand, require heating before catching fire. Understanding these distinctions is crucial for proper fire safety measures and the selection of appropriate firefighting equipment.
Therefore, the correct answer is A) Defines materials that burn at normal temperatures.