Because human behavior is unreliable and influenced by factors uncontrolled by policy, which domain represents the greatest risk and uncertainty to an organization?

The correct answer is letter "A": User Domain.

Explanation:

User Domains are used in organizations with large amounts of servers connected to their network. As it is difficult to keep track of all the data being stored in every server, the domain controller regulates user domains by storing their login credentials but having to pass a privilege screening before accessing to the information of the server. However, that does not secure users will make optimal utilization of the firm's resources. Most parts of the data store will still be unchecked by controllers.