The correct answer is: A. is Network Information Service
Network Information Service (NIS) is a client-server system that provides a centralized database of information for a network of computers. NIS was formerly known as Yellow Pages (YP). It allows users to access information such as user accounts, passwords, and group memberships from any computer on the network. NIS is a simple directory service that is easy to set up and use. It is a good choice for small to medium-sized networks.
Option B is incorrect. NIS is not a simple directory service. It is a complex system that provides a wide range of services.
Option C is incorrect. NIS was never known as Yellow Pages. Yellow Pages is a directory service that provides information about businesses and services. NIS is a directory service that provides information about users, groups, and other network resources.
Option D is incorrect. NIS does not allow configuration-such as password and group files. NIS provides a centralized database of information, but it does not allow users to modify that information.
Option E is incorrect. NIS is a real system that is used by many organizations. It is not a hypothetical system.