An Azure subscription contains Bastion1. You must support 100 concurrent SSH users on Bastion1 while minimizing management overhead. What should you do first?

Upgrading Bastion1 to the Standard SKU is the correct first step because the Basic SKU of Azure Bastion has a limitation of 5 concurrent SSH connections. To support 100 concurrent SSH users, you need the Standard SKU, which allows for significantly more concurrent connections and offers host scaling capabilities. Resizing the Bastion1 subnet is not directly related to the number of concurrent users. The subnet size determines the number of available IP addresses, not the Bastion host's capacity. Creating a network security group (NSG) is a security measure and doesn't increase Bastion's capacity. While host scaling is a feature of the Standard SKU that allows for more concurrent connections, you must first upgrade to the Standard SKU before you can enable and benefit from host scaling.