Which attribute of CARVER refers to how easily a terrorist can access a target?

The attribute of CARVER that refers to how easily a terrorist can access a target is indeed accessibility. Accessibility assesses the degree to which a target can be reached or approached by a terrorist. This factor is crucial in threat assessments because a target that is easily accessible poses a greater risk of being successfully attacked. Understanding accessibility helps in identifying soft targets or those with limited security measures in place, allowing for better risk management and protective strategies.

In contrast, recognizability focuses on how apparent or visible a target is to potential attackers, vulnerability pertains to the weaknesses that could be exploited during an attack, and reciprocity deals with the potential for retaliatory actions following an attack. Each of these attributes plays a role in the overall assessment of a target's risk, but accessibility specifically highlights the aspect of approachability, making it the correct choice in this context.