You have an Exchange Server 2010 organization. Your companys legal department sends compliance e-mail messages by adding recipients to the blindcarbon copy （Bcc） field. The companys compliance policy includes the following requirements： .All e-mail messages sent to external recipients must be archived in a central repository .Compliance officers must be able to identify all the recipients of archived e-mail messages You need recommend a solution to meet the compliance policy requirements. What should you recommend？（）

A. journal rules
B. message tracking
C. Personal Archives
D. transport rule