newbie: which server answers

[Yaro]

Hi,

I am trying to understand the idea of dns and I have
one simple (?) question:

let's say there is a domain named: domain.info and
there are four servers defined as authoritative
name servers for this domain. This information
is saved in root servers for top domain "info".
Each of these servers is correctly configured and ready
to give answers to dns-queries regarding domain.info.

the question is:
Which server will be queried by clients the most often?

Let's say their names are:
ns1.domain.info
ns2...
ns3...
ns4.domain.info
And there is no difference in their configuration
regarding domain.info.

Which of them is the most important (the most authoritative)?

Best regards
Jarek