The primary reason for an organization to include an acceptable use banner when users log in is to reduce the likelihood of insider threat, as it informs the users of the policies, rules, and expectations for the use of the organization's IT resources, and deters them from engaging in unauthorized or malicious activities. The other options are not the primary reasons, as they are more related to the detection, prevention, or mitigation of insider threat, respectively, rather than the reduction of the likelihood of insider threat. References = CRISC Review Manual, 7th Edition, page 155.