You need to ensure that the application login is unable to access other production databases

You administer a single server that contains a Microsoft SQL Server 2012 default instance.
You plan to install a new application that requires the deployment of a database on the server. The
application login requires sysadmin permissions.
You need to ensure that the application login is unable to access other production databases.
What should you do?

A.
Use the SQL Server default instance and configure an affinity mask.

B.
Install a new named SQL Server instance on the server.

C.
Use the SQL Server default instance and enable Contained Databases.

D.
Install a new default SQL Server instance on the server.