For setting up a NAS Server with Secure NFS, the following two configuration options are required:

NFSv4: This version of NFS includes support for strong security features and is designed to work well over the internet. NFSv4 has integrated security features and supports the Kerberos authentication protocol, which can provide a secure method for client-server interaction1.

UNIX Directory Service: This service is necessary for managing user and group information in a UNIX-like environment. It is essential for NFSv4 as it relies on this information for access control and mapping between users on the client and the server1.

The other options, such as NFSv3 (Option A), do not inherently support the same level of security features as NFSv4. User Mapping file (Option C) and DNS (Option D) are important for NFS configuration, but they are not specifically required for creating a NAS Server with Secure NFS. DNS is crucial for resolving hostnames to IP addresses, but it is not a security feature, and User Mapping file is more related to user identity mapping between different systems.

Therefore, the two required configuration options for creating a NAS Server with Secure NFS are NFSv4 and UNIX Directory Service, as they provide the necessary security and user management capabilities for a secure NFS setup.