Final answer:
An administrative unit in Microsoft 365 should be used to give Admin1 permission to manage users within the Human Resources department exclusively.
Step-by-step explanation:
To ensure that Admin1 has the necessary permissions to manage users specifically within the Human Resources department, you should use an administrative unit in Microsoft 365. Administrative units allow for the segregation of administrative roles and permissions within a larger organization. By creating an administrative unit for the Human Resources department and assigning Admin1 to manage that unit, you can scope their management capabilities to just that department.
To set this up in Microsoft 365:
Create an administrative unit and specify the Human Resources department as the scope.
Add Admin1 to the administrative unit as a member.
Assign the appropriate role to Admin1, such as User Management Administrator, but only within the context of the administrative unit.
This approach is more precise and secure compared to granting broader administrative permissions that could affect other departments.