Final answer:
The system property 'minimumRoleCount' ensures at least two users have the HR Admin role.
Step-by-step explanation:
The system property that ensures at least two users have the HR Admin role is called 'minimumRoleCount'.
This property is used in user management systems to specify the minimum number of users that should have a specific role, in this case, the HR Admin role.
For example, if the 'minimumRoleCount' property is set to 2, it means that there must be at least two users with the HR Admin role in the system.