We pick g.root-servers.net, one of the 13 root servers (1), and ask it about 31.94.in-addr.arpa and learn that in-addr.arpa is delegated to six name servers (2), so we ask a.in-addr-servers.arpa where we learn that 94.in-addr.arpa is delegated to six name servers, including sns-pb.isc.org (3), so we ask that one and get the following answer: