You have a computer named Client1. Client1 is joined to an Active Directory domain.
You need to join Client1 to an Azure Active Directory (Azure AD) tenant.
What should you do first?

A.
From the Local Group Policy Editor, modify the Add workstations to domain policy.

B.
From the network adapter properties, modify the DNS suffix.

C.
From System Control Panel, configure the computer to be a member of a workgroup.

D.
From the System in the Settings app, modify the sign-in options.

Explanation:
https://blogs.technet.microsoft.com/enterprisemobility/2015/05/28/azure-ad-join-on-windows-10-devices/