[CentOS] how do I find out which nameserver returns a DNS query?

Hi all

If I do a "dig mydomain.co.za" from a Linux server, how do I know which 
DNS nameserver returns the queries?

I seem to have a faulty DNS server, but can't see which one, so I want 
to find out which nameserver (if there's 4 - ns1.myserver, ns2.myserver, 
ns3.myserver & ns4.myserver) returns the queries?

-- 

Kind Regards
Rudi Ahlers
CEO, SoftDux

Web:   http://www.SoftDux.com
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