Which DNS record identifies the authoritative name server for a zone and governs caching parameters?

• A. SOA record defines primary name server and cache duration.
• B. A record maps domain to IP.
• C. MX record defines mail server.
• D. CNAME record aliases a name to another name.

Answer: (A)

The Start of Authority (SOA) record is the one that identifies which name server is authoritative for a DNS zone and also sets how long and how often information should be cached by resolvers. It includes the primary name server field, the zone administrator, a serial number, and the timing parameters that govern caching: refresh (how often to check for updates), retry (how long to retry if a transfer fails), expire (how long to keep data if the server becomes unavailable), and minimum TTL (how long records should be cached by resolvers).

Other common DNS records serve different purposes: an A record maps a domain to an IP address; an MX record specifies the mail server for email delivery; a CNAME record creates an alias from one name to another. None of these identify the authoritative source for the zone or govern caching behavior like the SOA record does.