The correct answer is B. ypbind.
ypbind is a client program that locates and binds to an NIS server. It is used to find and store information about an NIS domain and server.
A. ypwhich is a command-line utility that displays the name of the NIS server that is currently bound to.
C. ypcat is a command-line utility that displays the contents of an NIS map.
D. yppoll is a command-line utility that polls an NIS server for changes to its maps.
E. None of the above is a client program that finds and stores information about an NIS domain and server.