A `NOERROR` response contains authority evidence but no `AAAA` record for an existing nam…

A `NOERROR` response contains authority evidence but no `AAAA` record for an existing name. What does it mean?

1. NXDOMAIN: the name cannot have any record type
2. NODATA: the name exists but has no data of the requested type
3. SERVFAIL: every authoritative server timed out
4. A referral that must never be cached