Final answer:
The DNS resolver tool available on all major desktop operating systems is nslookup, which is used to query domain name servers for domain names and IP address mappings.
Step-by-step explanation:
The DNS resolver tool available on all major desktop operating systems is A) nslookup. The nslookup command allows users to query Internet domain name servers to obtain the mapping between domain names and IP addresses. This command is widely used for testing and troubleshooting DNS problems.
Dig (Domain Information Groper) is another DNS lookup utility, but it is not natively available on all operating systems, particularly Windows, without additional installation. Traceroute and ping are network diagnostic tools used for different purposes; traceroute is used to display the route and measure transit delays of packets across a network, and ping is used to check the reachability of a host on an Internet Protocol (IP) network.