Final Answer:
The action a DNS server takes if it does not have an entry for a requested URL is that it returns a “page not found” response to the client.option.b
Step-by-step explanation:
When a DNS server does not have an entry for a requested URL, it returns a “page not found” response to the client. This means that the DNS server cannot resolve the domain name to an IP address. The client then receives an error message indicating that the requested page cannot be found. This is a standard behavior of DNS servers when they are unable to locate the requested domain name in their records.
DNS servers do not drop the request or assign a temporary IP address to the name and send it to the client. Instead, they simply return an error message indicating that the requested page is not found. In some cases, the DNS server may also check with another DNS server to see if it has an entry for the requested URL, but the standard response when no entry is found is to return a “page not found” message to the client.
In summary, when a DNS server does not have an entry for a requested URL, it responds by returning a “page not found” message to the client, indicating that the requested page cannot be located.
Correct option is option.b