Which Azure service stores API keys, passwords, and certificates securely?

Azure Key Vault is the correct answer because it is a cloud service specifically designed to securely store and manage sensitive information such as API keys, passwords, certificates, and other secrets. It helps protect cryptographic keys and other secrets used by cloud applications and services. Azure AD (Active Directory) is an identity and access management service, not a secret storage solution. Azure Disk Storage provides block-level storage for Azure Virtual Machines, not secure secret management. Azure Policy is used to enforce organizational standards and assess compliance at scale, not to store secrets.