Your Azure subscription contains these unused resources: 20 Azure AD user accounts, five Azure AD groups, 10 public IP addresses, and 10 network interfaces. To reduce costs, which unused resources should you remove?

Public IP addresses incur charges even when not associated with a running resource. Removing unused public IP addresses directly reduces costs. Azure AD user accounts and groups do not typically incur direct costs themselves; their associated services might, but the accounts/groups are generally free up to a certain limit. Network interfaces, while a resource, usually only incur costs when attached to a running virtual machine or other compute resource; an unused, unattached network interface generally does not incur significant standalone charges. Therefore, public IP addresses are the most impactful resource to remove for cost reduction among the given options.