Answer:
B) Whois
Step-by-step explanation:
From the question we are informed about Clark who is a professional hacker. He targeted an organization for financial benefit and used various footprinting techniques to gather information about the target network. In this process, he employed a protocol used for querying databases that store the registered users or assignees of an Internet resource, such as a domain name, an IP address block, or an autonomous system.protocol employed by Clark in the above scenario is Whois.
WHOIS is can be regarded as query as well as response protocol which is been utilized broadly in querying databases that is responsible for storing of registered users as well as assignees of an Internet resource, these assignees could be domain name, it could be an IP address block as well as autonomous system, it can be utilized also as regards to wider range of other information