Your AD DS domain includes multiple domain controllers running Windows Server 2019 with configurations shown in an accompanying table. Before you run adprep /domainprep, which domain controller must be available for the command to succeed?

The adprep /domainprep command must be run on the domain controller holding the Infrastructure Master Flexible Single Master Operation (FSMO) role for the domain. This is because domainprep makes changes to the domain-wide application directory partitions, and the Infrastructure Master is responsible for updating object references between domains and ensuring consistency within the domain. If DC4 holds the Infrastructure Master role, it must be available. The other domain controllers (DC1, DC2, DC3) might hold other FSMO roles (like PDC Emulator, RID Master, Schema Master, or Domain Naming Master), but only the Infrastructure Master is critical for domainprep.