In Microsoft guidance, network segmentation and isolation are core security principles. Azure virtual networks (VNets) are "a fundamental building block... that enable isolation and segmentation of resources," and multiple VNets are commonly used to separate environments, business units, or security boundaries. This aligns with Zero Trust and SCI guidance that recommends isolating workloads to reduce blast radius and to apply least privilege and policy-based controls per boundary. Microsoft also emphasizes governance alignment, stating that enterprises should structure Azure resources so that policies, RBAC, and compliance requirements can be applied at appropriate scopes (management group, subscription, resource group, or network boundary). Deploying multiple VNets supports these goals by enabling per-environment policy assignment (for example, dev/test vs. production), differentiated security controls (such as NSGs, ASGs, and firewalls), and independent address spaces to prevent overlap across organizations or regions. Options A and D are not primary drivers: budgeting is handled at subscription/resource group scopes rather than VNet count, and a single VNet can already host and connect many resource types; creating multiple VNets is therefore primarily about governance and isolation that reduce risk and enforce organizational policies.