Which feature does Windows Server support to ensure reliability through redundancy?

Windows Server includes fault-tolerant features that are specifically designed to enhance reliability through redundancy. These features can include technologies like failover clustering, which allows multiple servers to work together so that if one fails, another can take over with minimal disruption. This redundancy is essential in critical applications and services, ensuring continuity and availability.

Other options, while beneficial in certain contexts, do not directly contribute to reliability through redundancy. For instance, Network Address Translation (NAT) primarily focuses on IP address management and security rather than fault tolerance. Antivirus scanning plays a crucial role in protecting a system from malware but does not inherently provide redundancy. Online data backup is important for data safety in case of loss but does not offer immediate redundancy during system operation. Therefore, the best choice that encapsulates the concept of ensuring reliability through redundancy is the fault-tolerant features provided by Windows Server.