What should you do?

You have an Azure Active Directory (Azure AD) tenant named contoso.onmicrosoft.com.
You hire a temporary vendor. The vendor uses a Microsoft account that has a sign-in of [email protected].
You need to ensure that the vendor can authenticate to the tenant by using [email protected].
What should you do?
A. From the Azure portal, add a custom domain name, create a new Azure AD user, and then specify [email protected] as the username.
B. From Azure Cloud Shell, run the New-AzureADUser cmdlet and specify the -UserPrincipalName [email protected] parameter.
C. From the Azure portal, add a new guest user, and then specify [email protected] as the email address.
D. From Windows PowerShell, run the New-AzureADUser cmdlet and specify the -UserPrincipalName [email protected] parameter.