b.ROOT-SERVERS.NET has no CNAME records.
Question and response
Question
dig b.ROOT-SERVERS.NET. NS
Answer
The response has no answer records.
Authority
ROOT-SERVERS.NET. 5548 SOA a.ROOT-SERVERS.NET. nstld.verisign-grs.com. 2026021900 14400 7200 1209600 3600000
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0