Identify one biological toxin used in bioweaponry.

Botulinum toxin is considered a biological toxin used in bioweaponry due to its potency and lethality. It is produced by the bacterium Clostridium botulinum and causes botulism, a serious illness that can lead to paralysis and respiratory failure. The lethality of botulinum toxin is extremely high; even a tiny amount can be fatal if ingested or injected. Because of these properties, it has been studied and considered for use in bioweapons.

In contrast, while ricin is also a biological toxin derived from castor beans and has been used in assassination attempts, botulinum toxin's extreme potency often makes it a more focused agent in theoretical bioweapon applications. Hemlock is a plant with toxic compounds, but it is less commonly associated with bioweaponry. Arsenic, although toxic, is classified as a chemical agent rather than a biological one, which further highlights how botulinum toxin fits the category of biological toxins in the context of warfare.