The correct answer is C.
OBJ-3.5: In this scenario, the only one of these techniques we know was used for certain is a proof of concept. A proof of concept is a benign exploit developed to highlight vulnerabilities in a system or product. Usually, a proof of concept is developed by security researchers to demonstrate a flaw of vulnerability in a widely used system, software, hardware, or protocol. The technical details may not be initially published until the researcher can provide the information to the companies affected, and they can release a patch. Other times, the security researchers will provide all the details in their security blogs so that both defenders and attackers know the exploit’s details.