What should you do?

Your network contains an on-premises Active Directory domain named contoso.local that has a forest functional level of Windows Server 2008 R2.

You have a Microsoft 365 E5 subscription linked to an Azure Active Directory (Azure AD) tenant named contoso.com.

You plan to install Azure AD Connect and enable single sign-on (SSO).

You need to prepare the domain to support SSO. The solution must minimize administrative effort.

What should you do?
A . Raise the forest functional level to Windows Server 2016.
B. Modify the UPN suffix of all domain users.
C. Populate the mail attribute of all domain users.
D. Rename the domain.

Answer: B

Explanation:

Reference: https://docs.microsoft.com/en-us/microsoft-365/enterprise/prepare-a-non-routable-domain-for-directory-synchronization?view=o365-worldwide