Which of the following is required by Microsoft's Active Directory Migration Tool (ADMT)?

The Active Directory Migration Tool (ADMT) requires SQL Server to function effectively. This tool facilitates the migration of user accounts, groups, and computers from one Active Directory domain to another, particularly when these domains are in different forests. SQL Server serves as the database backend that stores the necessary data during the migration process, helping ensure that users and their attributes are transferred accurately and efficiently.

Using SQL Server allows ADMT to leverage its robust capabilities for managing relational data, which is essential for handling the complexities of user account management during migration. The other database systems listed, such as MySQL, Oracle, and PostgreSQL, are not compatible with ADMT as it is specifically designed to operate with SQL Server for these functions. This design choice ensures that organizations have a seamless experience when migrating their Active Directory environments.