An organization plans to migrate to Office 365. You use the Windows Azure Active Directory (AD) Sync tool.
Several users will not migrate to Office 365. You must exclude these users from synchronization. All users must continue to authenticate against the on-premises
Active Directory.
You need to synchronize the remaining users.
Which three actions should you perform? Each correct answer presents part of the solution.

A.
Populate an attribute for each user account.

B.
Disable the user accounts in Active Directory.

C.
Perform a full synchronization.

D.
Configure the connection filter.

E.
Run the Windows PowerShell command Set-MsolDirSyncEnabled -EnableDirSync $false.

Explanation:

http://www.proexchange.be/blogs/office365/archive/2011/07/28/modify-dirsync-to-not-sync-all-users-to-office-365.aspx