Final answer:
When a DNS server returns a referral to a client, it is engaging in iterative resolution, providing the client with greater control over the query process by leading them to the next server that can assist them further.
Step-by-step explanation:
When a DNS name server returns a referral to a client as its response to a name query, it is using iterative resolution. In iterative resolution, the DNS server provides the best information it has to help the client reach its destination but does not perform the query on behalf of the client. Instead, it refers the client to another DNS server closer to the information it needs. This allows the client to have more control over the resolution process, as it needs to contact the referred DNS server itself. The iterative protocol, unlike recursive resolution, does not involve the server continuing to resolve the query through other DNS servers on behalf of the client. So, the correct answer is b) Iterative; for more control over the resolution process.