Lashonda sets up a DNS server, SERVER$1,$ with a forward lookup zone called domainA.com. It hosts the resource records for the domainX.com Active Directory domain. It contains host $($A$)$ records for two network interfaces on SERVER$1(172\mathrm{.}16\mathrm{.}0\mathrm{.}10$ and $192\mathrm{.}168\mathrm{.}1\mathrm{.}50).$ The host records are associated with the FQDNs server$1.$domainA.com and domainA.com. There is also an SOA record and an NS record for the zone.

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Which of the following records identifies SERVER$1$ as an authoritative DNS server?

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a$.$

The SOA record

b$.$

The NS record$$

c$.$

The A record for $172\mathrm{.}16\mathrm{.}0\mathrm{.}10$

d$.$

The A record for $192\mathrm{.}168\mathrm{.}1\mathrm{.}50$