Final answer:
To delegate permissions for the users in a single department on Microsoft Entra, you should use an Administrative Unit. This feature allows for localized management of users and specific departmental permissions without impacting other areas of the organization.
Step-by-step explanation:
To delegate permissions for the users in a single department using Microsoft Entra (formerly Azure Active Directory), you should use an Administrative Unit. Administrative Units are containers within Azure AD that enable fine-grained delegation of administrative roles and allow for more localized administration of users. With an Administrative Unit, you can grant department-specific permissions without affecting other departments or the entire tenant.
While a Security Group is often used for granting access to resources, they aren't meant to delegate administrative permissions. Resource Groups are used within Azure to manage resources, but do not apply to user account management. Finally, a Workspace is not a relevant concept in this context as it generally pertains to a grouping within an application or service for collaboration and is not used for Azure AD user management.