You have several virtual networks; each virtual network contains 20 internet-accessible resources assigned public IP addresses. You need to protect these resources using Azure DDoS Network Protection while minimizing cost. What is the minimum number of DDoS Network Protection plans you should deploy?

Azure DDoS Network Protection plans are billed per protected virtual network. While a single DDoS Protection plan can protect multiple virtual networks across regions and subscriptions, each virtual network that you want to protect must be explicitly linked to the plan. The question states you have "several virtual networks," implying more than one, and each needs protection. To minimize cost, you should create one DDoS Protection Plan and link all the virtual networks to it. However, the question also specifies "20 internet-accessible resources assigned public IP addresses" within each virtual network. This implies that each virtual network is a separate entity requiring protection. Therefore, to protect all resources across these "several virtual networks," you would need one plan per virtual network, resulting in 2 plans.