Which of the following is classified as a Class D extinguishing agent?

A Class D extinguishing agent is specifically designed to combat fires that involve combustible metals, such as magnesium, titanium, and sodium. These types of fires cannot be extinguished effectively with conventional agents like water or foam, as they can react violently with such substances.

Dry powder extinguishing agents, such as sodium chloride, are formulated to smother and cool these metal fires, inhibiting their ability to combust. This makes them essential for tackling fires in certain industrial and manufacturing environments where these metals are present. Other agents in the options, like foam, carbon dioxide, and water mist, are inappropriate for Class D situations and could exacerbate the fire risk instead of mitigating it. This highlights the critical role of specialized agents like dry powder in fire safety protocols for hazardous materials.