Which appendix of ATP 2-01.3 contains threat characteristics for irregular threats?

The correct choice highlights that Appendix C of ATP 2-01.3 specifically addresses threat characteristics for irregular threats. This appendix provides essential information and details about the nature, behavior, and capabilities of various irregular threats, which typically include non-state actors, insurgent groups, and other entities that do not conform to conventional warfare norms. Understanding these characteristics is crucial for military and strategic planning, as irregular threats often require different tactics and approaches compared to traditional, regular military adversaries. By focusing on these characteristics, military planners can better anticipate potential challenges and devise appropriate responses when engaging with irregular threats.