A company deploys an Office 365 tenant. You install the Active Directory Federation Services (AD FS) server role on a server that runs Windows Server 2012. You
install and configure the Federation Service Proxy role service. Users sign in by using the Security Assertion Markup Language (SAML) protocol.
You need to customize the sign-in pages for Office 365.
Which pages should you customize? To answer, drag the appropriate page to the correct customization. Each page may be used once, more than once, or not at
all. You may need to drag the split bar between panes or scroll to view content.
Answer: 
Explanation:
http://msdn.microsoft.com/en-us/library/ee895359.aspx
HomeRealmDiscovery.aspx
Presents a selection UI for the user to select the organization to which he or she belongs.
FormsSignIn.aspx
Handles Form-based authentication with user name and password.
SignOut.aspx
Handles Sign-Out requests.
IdpInitiatedSignOn.aspx
Presents a selection UI for the user to select an RP application to sign in to. This page only works for RP applications that use the SAML protocol.
Error.aspx
Displays authentication errors to the user.
MasterPages/MasterPage.master
A master page template for all the pages.