Name three common DNS record types and their purposes.

• A. A maps IPv4 to IPv6; AAAA maps to IPv4 address; CNAME specifies mail servers
• B. A maps hostname to IPv4 address; AAAA maps to IPv6 address; CNAME aliases one name to another; MX specifies mail servers.
• C. TXT holds binary executable; SRV stores video files
• D. NS record defines mail servers; PTR maps IPv4 addresses to hostnames

Answer: (B)

DNS records tell systems how to reach services for a domain. An A record links a hostname to its IPv4 address, so clients know where to connect on the IPv4 network. An AAAA record does the same for an IPv6 address. A CNAME record creates an alias from one name to another, allowing multiple names to refer to the same resource. An MX record specifies which mail servers are responsible for handling email for the domain. This combination reflects common, real-world uses of DNS: forward mapping to addresses for web traffic, an IPv6 counterpart, aliasing to simplify naming, and directing email delivery to the correct servers. The other descriptions misstate how these records work—for example, suggesting A maps IPv4 to IPv6 or that CNAME is for mail servers, or mischaracterizing TXT and SRV or reverse DNS records.