You are the administrator for a company named Contoso, Ltd. The company has an Office 365 subscription.

Your need to prevent users from changing their user display name by using Outlook Web App.
What should you do?

A.
Run the Set-MsolCompanyContactInformation cmdlet.

B.
Modify the default email address policy.

C.
Run the Set-MsolUserPrincipalName cmdlet.

D.
Modify the default role assignment policy.

Explanation:
http://help.outlook.com/en-us/140/ff852817.aspx