Which of the following is a requirement for creating a restricted group policy?

Creating a restricted group policy requires that the group is already defined within Active Directory. This is crucial because Group Policy Objects (GPOs) are mechanisms that apply settings to defined security groups, and if the group does not exist in Active Directory, there's no target for the policy to apply to.

Having a pre-existing group allows the Group Policy to enforce membership settings, permissions, or other configurations as intended. This step ensures that the necessary security context is in place within the Active Directory structure to manage user roles and permissions effectively.

The other options do not accurately represent requirements for restricted group policies. For instance, while the name "Administrators" may imply specific functions related to administrative access, it does not serve as a general requirement for creating a restricted group. Furthermore, there’s no stipulation that a group must belong to a specific Organizational Unit or that it can have only a limited number of members, allowing for flexibility in how Active Directory groups are configured and utilized in different policies.