The VCF 9.0 Operations Documentation identifies Operations for Networks as the key enabler for the Network Operations feature:
"VCF Operations for Networks (formerly vRNI) provides visibility into network traffic flows, NSX fabric health, application dependency mapping, and micro-segmentation planning. It integrates directly into VCF Operations dashboards under Network Operations." The vDefend firewall is unrelated, as it provides workload-level security. The VCF Operations Collector is required for telemetry ingestion but does not provide full Network Operations. NSX itself provides the underlying virtual networking, but it must be monitored through VCF Operations for Networks. Therefore, the correct answer is VCF Operations for Networks.