To satisfy the technical requirements for backing up Server4, what should you do first?

The Microsoft Azure Recovery Services (MARS) agent is the correct first step because it enables direct backup of files, folders, and system state to Azure Recovery Services vaults. This agent is specifically designed for granular backup of individual servers and is a prerequisite for using Azure Backup for on-premises Windows Servers. Deploying MABS is a more comprehensive solution for multiple servers and applications, but the MARS agent is needed for direct server backup. Windows Server Backup is an on-premises solution and doesn't directly integrate with Azure for cloud backups. Storage Replica is for disaster recovery and high availability, not for backing up data to Azure.