Contoso, Ltd. plans to use Office 365 for email services and Lync Online. Contoso has four unique domain names.
You need to migrate domain names to Office 365.
Which two domain names should you exclude from the migration? Each correct answer presents part of the solution.

A.
contoso.us

B.
contoso

C.
contoso.local

D.
contoso.co

Explanation:
contoso.us – valid TLD Domain
contoso.co – valid TLD Domain
contoso – single labeled domain – not valid
contoso.local – internal labeled domain – not valid
http://technet.microsoft.com/en-us/library/hh852440.aspx
You need to add and verify a domain only once. If someone else in your organization has already added and verified the same domain, you can’t add the domain
again.
You can add multiple domains to Office 365, but each domain has to have a valid Internet domain suffix, such as .com, .co, .net, .org, or a country code.
Here are some examples:
· Supported: contoso.com
· Supported: contoso.us
· Not supported: contoso
· Not supported: contoso.local