You have a hosted Exchange organization. All servers in the organization have Exchange
Server 2010 Service Pack 1 (SP1) installed.
All users use Microsoft Outlook 2010.
A user named User1 reaches her mailbox size limit.
You need to ensure that User1 can archive e-mail messages located in her mailbox and
read the archived messages when she works offline.
What should you create for User1?

A.
a managed folder mailbox policy

B.
a personal folder (PST) file

C.
a Personal Archive

D.
an offline store (OST) file

Explanation:
Clue is in the

QUESTION she needs

to be able to read them offline, but for them to not remain in her Inbox.