Which of the following is NOT one of the six types of chemical agents?

The selection of "C. Explosive" as the option that is NOT one of the six types of chemical agents is justified because the six classifications of chemical agents primarily focus on those designed for incapacitation, injury, or death caused by chemical reactions in biological organisms. The recognized types include nerve agents, blood agents, choking (or pulmonary) agents, blister agents, incapacitating agents, and riot control agents. Explosives, however, are classified separately as they are primarily chemical compounds that produce a destructive force through rapid chemical reactions, not specifically for causing harm through toxicological means. Thus, "C. Explosive" clearly stands apart from the classification of chemical warfare agents, making it the correct choice.