Answer: an Azure Key Vault

Azure Disk Encryption requires Azure Key Vault to securely store and manage the disk encryption keys and secrets. The community discussion shows 100% consensus on option B, with multiple comments citing Microsoft documentation that explicitly states Azure Key Vault must be created first before enabling disk encryption. The Key Vault serves as the central repository for encryption keys, which is a prerequisite for the encryption process. While an encryption key (option D) is needed, it is stored within the Key Vault, making the vault itself the foundational resource. Azure Storage account (option A) is not required for disk encryption of existing VMs, and Azure Information Protection policy (option C) is unrelated to disk-level encryption.

Author: LeetQuiz Editorial Team