You need to ensure that User1 can use Windows Server Backup to back up Server1

Your network contains an Active Directory domain named contoso.com. The domain
contains a file server named Server1 that runs Windows Server 2012 R2.
You create a user account named User1 in the domain.
You need to ensure that User1 can use Windows Server Backup to back up Server1. The
solution must minimize the number of administrative rights assigned to User1.
What should you do?

A.
Add User1 to the Backup Operators group.

B.
Add User1 to the Power Users group.

C.
Assign User1 the Backup files and directories user right and the Restore files and
directories user right.

D.
Assign User1 the Backup files and directories user right.

Explanation:
http://technet.microsoft.com/en-us/library/cc787956(v=ws.10).aspx
http://technet.microsoft.com/en-us/library/cc756898(v=ws.10).aspx
http://technet.microsoft.com/en-us/library/cc771990.aspx
Backup Operators have these permissions by default:

However the question explicitly says we need to minimize administrative rights. Since the
requirement is for backing up the data only–no requirement to restore or shutdown–then
assigning the “Back up files and directories user right” would be the correct answer.