What command can resolve failed health checks on a deployed HTTP(s) Load Balancer for port 80?

The action required to resolve failed health checks on a deployed HTTP(s) Load Balancer for port 80 typically involves ensuring that the load balancer has proper access to the backend instances that it needs to check. Creating a firewall rule to allow traffic from the load balancer to the backend instances is essential in this scenario.

In this case, option C focuses on creating a firewall rule that allows TCP traffic through the designated network. This is critical because health checks from the load balancer must have the necessary permissions to access the backend instances on the relevant port, which is 80 for HTTP. By specifying the source ranges or IP addresses utilized by the load balancer, traffic can flow freely, thereby facilitating successful health checks.

Other options involve adding access configurations, tags, or setting destination ranges, which do not directly address the root issue of enabling the network connectivity necessary for health checks. These options may focus on instance configurations or tagging but fail to ensure that the load balancer can effectively communicate with the backend, which is the key requirement to resolve the health check failures. Thus, establishing a proper firewall rule that specifically allows the necessary traffic is the most effective resolution in this context.