Final answer:
Water can be used on Class A fires but not Class D fires due to the risk of a violent reaction. AFFF is suitable for Class A fires but not for Class D fires. PKP is not recommended for either Class A or Class D fires.
Step-by-step explanation:
To determine which extinguishing agents should be used for Class A or Class D fires, we need to consider the properties of the fires and the agents. Class A fires involve ordinary combustibles like wood, paper, and textiles. Class D fires involve combustible metals. Water is generally effective for Class A fires but should not be used on Class D fires due to the risk of a violent reaction. An Aqueous Film Forming Foam (AFFF) can be used on Class A fires due to its cooling and smothering properties, but it is not suitable for Class D fires. Potassium Bicarbonate (PKP), which is a dry chemical agent, is not the correct choice for Class A fires, and it is also not recommended for Class D fires. The best extinguishing agents for Class D fires are specialized Class D extinguishers, which are not on the list provided. Therefore, among the options given, only AFFF should be used for Class A fires. No agent from the list provided should be used for Class D fires.