Which of the following is an example of a blood agent?

The choice of arsine as an example of a blood agent is correct because blood agents are toxic chemicals that primarily affect the body's ability to use oxygen, leading to asphyxiation at the cellular level. Arsine is a recognized blood agent, functioning by binding to hemoglobin in the blood and inhibiting its capacity to transport oxygen, which can result in severe poisoning and potentially death.

In contrast, other options refer to different classes of chemical agents. VX is a nerve agent that disrupts the normal functioning of the nervous system. Distilled mustard, commonly known as mustard gas, is a blistering agent that causes severe skin and respiratory damage. Tabun is another type of nerve agent similar to VX. Each of these agents operates through distinct biological mechanisms that do not pertain to the definition of blood agents, highlighting the unique characteristics of arsine within the context of chemical warfare.