Your organization contains two Windows Server 2003 servers named Server1 and Server2 that run Exchange Server 2003.
Server1 is configured as a back-end server. Server2 is configured as a front-end server and is the only server that is accessible from the Internet.
Users frequently access their mailboxes from public computers by using Microsoft Office Outlook Web Access (OWA).
You need to ensure that idle OWA sessions are automatically closed.
What should you enable?

A.
digest authentication on Server1

B.
digest authentication on Server2

C.
form-based authentication on Server1

D.
form-based authentication on Server2