Correct Answer: CThe described scenario illustrates the social engineering technique known as tailgating. Tailgating involves an unauthorized individual following an authorized person into a secure building without providing their own credentials for access. In this scenario, the unknown individual engages in conversation and takes advantage of the employee's access by holding the door open when the employee scans their badge, thus gaining unauthorized entry. This aligns with the definition of tailgating, whereas shoulder surfing involves observing someone’s private information over their shoulder, which is not depicted in this instance.