You are deploying two network virtual appliances (NVAs) inside an Azure virtual network to inspect all traffic within the VNet. The solution must provide high availability for the NVAs while minimizing administrative overhead. Which Azure service should you include to meet these requirements?

Azure Standard Load Balancer is the correct choice because it operates at Layer 4 (TCP/UDP) and can distribute traffic between multiple NVA instances within a VNet. This provides high availability by directing traffic to healthy NVAs and failing over if one becomes unhealthy. Its VNet-internal deployment and health probe capabilities make it ideal for NVA high availability with minimal administrative overhead. Azure Application Gateway operates at Layer 7 (HTTP/S) and is designed for web traffic, not general network traffic inspection by NVAs. Azure Traffic Manager and Azure Front Door are global DNS-based load balancing services, operating outside of a single VNet, and are used for directing traffic to endpoints across regions or globally, not for internal VNet NVA high availability.