Before adding VM1 and VM2 to LB1’s backend pool, what must you do first?

Azure Load Balancers require backend pool VMs to be in the same availability set or virtual machine scale set for high availability and proper load distribution. Redeploying VM1 and VM2 to the same availability set ensures they are placed in different fault domains and update domains within the same datacenter, making them eligible for the load balancer's backend pool. Connecting VM2 to VNET1/Subnet1 is necessary for network connectivity but doesn't address the availability requirement for the load balancer. Redeploying to the same availability zone is not a prerequisite for a standard load balancer, though it can be a design choice for zonal redundancy. Creating a new NSG and associating it to VNET1/Subnet1 is for network security, not a prerequisite for load balancer backend pool membership.