Which amongst the following biological agents has the highest potential for use as a biological weapon for microbial bioterrorism -

Plague, smallpox and Botulinum all belong to category 'A' agents of microbial bioterrorism as classified by U.S. Centre for Disease Control and Prevention (CDC). All these agents represent 'high' risk to national security and represent potentially dangerous agents as biological weapons. ‘The highly contagious nature and high mortality of plague make it a close to an ideal agent of bioterrorism, particularly if delivered in a weaponized form.'