问题：
[单选] You work as a network Exchange administrator at Company.com.The Company.com network currently consists of a single Active Directory forest containing a single domain named Company.com.The Company.com organization makes use of Microsoft Exchange Server 2010 as their messaging solution.you are responsible for managing three mailbox servers named - ex01， -ex02 and -ex03.during the course of the week you receive an instruction from management to configure a journaling mailbox on ex03 as well as to configure journaling on various mailboxes in -ex01 and -ex02.to ensure productivity you need to make sure that journaling will continue to happen in the event that -ex03 failing.What should you do？（）
A . Your best option would be to create a retention tag.Thereafter the tag needs to be assigned to the new retention policy.
B . Your best option would be to have the shadow redundancy settings confnfigured in the organization.
C . your best option would be to have an alternate journaling mailbox configured on -ex02.
D . Your best option would be to have a second e-mail address configured for the journaling mailbox.
