You need to prevent a user named User1 from permanently deleting an email message in his mailbox

You have an Exchange Server 2013 organization.
You need to prevent a user named User1 from permanently deleting an email message in his
mailbox.
What should you do on the mailbox of User1?

A.
Implement a retention policy.

B.
Configure a retention hold.

C.
Implement a data loss prevention (DLP) policy.

D.
Configure an in-place hold.

Explanation:
In Exchange 2013, you can use In-Place Hold to accomplish the following goals:
Place user mailboxes on hold and preserve mailbox items immutably
Preserve mailbox items deleted by users or automatic deletion processes such as MRM
Use query-based In-Place Hold to search for and retain items matching specified criteria
Preserve items indefinitely or for a specific duration
Place a user on multiple holds for different cases or investigations
Keep In-Place Hold transparent from the user by not having to suspend MRM
Enable In-Place eDiscovery searches of items placed on hold