Your network contains an Active Directory domain named contoso.com. All domain controllers run
Windows Server 2012 R2. The domain contains two domain controllers.
The domain controllers are configured as shown in the following table.

You configure a user named User1 as a delegated administrator of DC10.
You need to ensure that User1 can log on to DC10 if the network link between the Main site and the
Branch site fails.
What should you do?

A.
Add User1 to the Domain Admins group.

B.
On DC10, modify the User Rights Assignment in Local Policies.

C.
Run repadmin and specify the /prp parameter.

D.
On DC10, run ntdsutil and configure the settings in the Roles context.

Explanation:
repadmin /prp will allow the password caching of the local administrator to the RODC.
This command lists and modifies the Password Replication Policy (PRP) for read-only domain
controllers (RODCs).

RODC Administration
https://technet.microsoft.com/en-us/library/cc755310%28v=ws.10%29.aspx