To perform a bulk delete of users in Azure Active Directory, you need to create and upload a CSV file that contains the list of users to be deleted. The file should include the user principal name (UPN) of each user only. Therefore, the answer is B. The user principal name of each user only. When you use the bulk delete feature in the Azure Active Directory admin center, you need to specify the UPN for each user that you want to delete. The UPN is a unique identifier for each user in Azure AD and is the primary way that Azure AD identifies and manages user accounts. Including additional attributes like the display name or usage location is not required for the bulk delete operation, as the UPN is the only mandatory attribute for the user account. However, you may include additional attributes in the CSV file if you want to keep track of the metadata associated with each user account.