You need to add a third email address for each user

Your network contains an Active Directory domain named contoso.com. The domain contains Windows 10
Enterprise client computers.
Your company has a subscription to Microsoft Office 365. Each user has a mailbox that is stored in Office 365
and a user account in the contoso.com domain. Each mailbox has two email addresses.

You need to add a third email address for each user.
What should you do?

A.
From Active Directory Users and Computers, modify the E-mail attribute for each user.

B.
From Microsoft Azure Active Directory Module for Windows PowerShell, run the Set-Mailbox cmdlet.

C.
From Active Directory Domains and Trust, add a UPN suffix for each user.

D.
From the Office 365 portal, modify the Users settings of each user.