Which DNS record type maps a hostname to an IPv4 address?

Correct answer: A record

Option A is correct because the DNS A record (Address record) is the fundamental record type that maps a fully qualified domain name to a 32-bit IPv4 address, enabling clients to resolve hostnames to IP addresses for routing purposes. Option B is wrong because a CNAME (Canonical Name) record creates an alias from one hostname to another hostname, not a direct mapping to an IP address. Option C is wrong because a PTR (Pointer) record performs the reverse function, mapping an IP address back to a hostname, used in reverse DNS lookups. Option D is wrong because an MX (Mail Exchanger) record specifies the mail servers responsible for accepting email for a domain, not hostname-to-IP address resolution.