Hi, The question is little bit offtopis but I hope that you will forgive me.
DNS responce contain additional records there could be some additional informations that DNS server sends to the client. The case is that DNS is dual stack and the user is the IPv4 only (it does not know what IPv6 is). In the additional informations is part with IPv6 address and AAAA. Will the client ignore such information if it does not know what they are (and not so importannt) or what?
"DNS is dual stack" is not specific enough.
I suggest you study draft-ietf-dnsop-ipv6-dns-issues-10.txt -- it should provide the pointers to answer your DNS query. :)
-- Pekka Savola "You each name yourselves king, yet the Netcore Oy kingdom bleeds." Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings