The correct answer is C.
OBJ-4.2: 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. OpenVas, SET, and Aircrak-NG are not considered OSINT tools. OpenVas is a vulnerability scanner. SET is a social engineering tool. Aircrack-NG is a wireless hacking tool.