You have an Exchange Server 2013 organization.
A user is involved in a possible litigation matter.
You need to protect all of the messages in a mailbox from permanent deletion.
Which cmdlet should you use?

A.
Enable-InboxRule

B.
Add-MailboxPermisssion

C.
Set-Mailbox

D.
Set-Retention Policy

Explanation:
This example configures April Stewart’s mailbox to retain deleted items for 30 days.
Set-Mailbox -Identity – “April Stewart” -RetainDeletedItemsFor 30
Note: When a user deletes items from the Deleted Items default folder by using the Delete, Shift+Delete, or
Empty Deleted Items Folder actions, the items are moved to the Recoverable Items\\Deletions folder. The
duration that deleted items remain in this folder is based on the deleted item retention settings configured for
the mailbox database or the mailbox.
Incorrect:
Not D: The Set-Retention Policy is used in a cloud environment only.
Configure Deleted Item retention and Recoverable Items quotas
https://technet.microsoft.com/en-us/library/ee364752%28v=exchg.150%29.aspx