The correct answer is A.
OBJ-3.3: Shodan (shodan.io) is a search engine that identifies Internet-connected devices of all types. The engine uses banner grabbing to identify the type of device, firmware/OS/app type, and version, plus vendor and ID information. This involves no direct interaction with the company’s public-facing internet assets since this might give rise to detection. This is also the first place an adversary might use to conduct reconnaissance on your company’s network. The nmap scanning tool can provide an analysis of the current state of public exposure but has no mechanism to determine the history, nor will it give the same depth of information that shodan.io provides. Google Hacking can determine if a public exposure occurred over public-facing protocols, but it cannot conclusively reveal all the exposures present. Google hacking relies on using advanced Google searches with advanced syntax to search for information across the internet. Network diagrams can show how a network was initially configured. Unless the diagrams are up-to-date, which they usually aren’t, they cannot show the current “as is” configuration. If you can only select one tool to find your attack surface’s current and historical view, shodan is your best choice.