Which statement best describes the DNS resolution algorithm order?

• A. The resolver contacts root name servers; asks the TLD name server for the authoritative name server for the domain; if subdomains exist, repeats this process on the authoritative server for every subdomain; finally, the resolver asks for the host part
• B. The resolver queries only the root name servers
• C. The resolver asks only the authoritative name server for the domain
• D. The resolver contacts root name servers; asks the TLD name server for the domain's authoritative server; if there are subdomains, repeats the process on the authoritative server; finally, the resolver asks for the host part

Answer: (D)

DNS resolution follows a hierarchical chain of referrals, moving from the root down to the specific zone that contains the host record. A resolver begins at the root name servers, which refer it to the appropriate top-level domain (TLD) name server for the domain. The TLD server then directs the resolver to the domain’s authoritative name server. If there are subdomains, the authoritative server for the domain may refer the resolver to the next level’s authoritative server, and this process continues down the hierarchy until the zone containing the host is reached. At that point, the resolver queries for the host’s address (A or AAAA record).

This description matches the chosen option because it accurately outlines the root → TLD → domain authoritative server path, the potential descent through subdomains, and the final lookup for the host record. The other choices either omit essential steps, oversimplify, or miss part of the referral chain.