Which Cisco operating systems support YANG data models, NETCONF, RESTCONF, and gRPC?

The chosen answer identifies the Cisco operating systems that support YANG data models, NETCONF, RESTCONF, and gRPC, which are essential protocols and data modeling languages used in network automation and management.

Cisco IOS XE, Cisco NX-OS, and Cisco IOS XR are designed with modern network programmability and automation capabilities in mind. They offer robust support for YANG data models, allowing for the structured representation of device configurations and states. NETCONF and RESTCONF provide methods for network device management and configuration, with NETCONF being a protocol that manages network devices over SSH and RESTCONF allowing for communication over HTTP using RESTful principles. Additionally, gRPC is a high-performance RPC framework that is also supported to facilitate communication across various services and applications.

This combination of operating systems and their capabilities aligns with the need for automation in contemporary network environments, making option A the comprehensive choice regarding programmability and automation support in Cisco's ecosystem. Other options do not represent operating systems known for these advanced features, focusing instead on older or different types of Cisco devices that lack these modern programmability protocols.