The correct answer is C. /etc/nsswitch.conf
The /etc/nsswitch.conf file specifies the order in which to use specified name services. It is a configuration file that tells the system where to look for information about users, groups, hosts, and services.
The /etc/services file contains a list of well-known ports and their associated services. It is used by the operating system to resolve host names to IP addresses.
The /etc/hosts file contains a list of IP addresses and their associated host names. It is used by the operating system to resolve host names to IP addresses.
The /etc/nsorder file is not a valid option.