You need to prevent User1 from permanently deleting items from his mailbox

You have an Exchange Server 2010 organization named contoso.com. Your company is
investigating a user named User1.
You need to prevent User1 from permanently deleting items from his mailbox.
What should you run?

A.
Set-Mailbox User1 LitigationHoldEnabled $true.

B.
Set-Mailbox User1 ModerationEnabled $true.

C.
Set-Mailbox User1 RetainDeletedItemsUntilBackup $true.

D.
Set-Mailbox User1 RetentionHoldEnabled $true.