VNet1, VNet2, and VNet3 are peered. You will use Azure Bastion to provide secure administrative access to all session hosts while minimizing cost. How many Azure Bastion hosts should you deploy?

You should deploy 1 Azure Bastion host. When VNets are peered, resources in one VNet can communicate with resources in another VNet. Azure Bastion can be deployed in a central VNet (e.g., VNet1) and, through VNet peering, provide secure administrative access to virtual machines (session hosts) in all peered VNets (VNet1, VNet2, and VNet3). This minimizes cost by avoiding redundant Bastion deployments. Deploying 2, 3, or 4 Bastion hosts would be unnecessary and more expensive, as a single Bastion host can serve all peered VNets.