Final answer:
Class D fires involve combustible metals; these are high-temperature fires that require special Class D fire extinguishers to put out.
Step-by-step explanation:
Class D fires involve combustible metals, such as magnesium, titanium, zirconium, sodium, lithium, and potassium, among others. These types of fires are known for their high temperatures and the unique challenges they present in terms of suppression and extinguishing. Because they involve metals that can react with water or other common firefighting agents, extinguishing them requires specific Class D fire extinguishers which typically contain dry powder agents that can cool and smother the fires without causing reactions that might exacerbate the situation.