Which of the following best characterizes the function of a physical access control?

The function of physical access control is best characterized by the separation of unauthorized individuals from computer resources. This system is designed to limit access to physical locations where sensitive information or critical hardware is stored, ensuring that only authorized personnel can enter these areas. By implementing measures such as locks, security guards, key cards, or biometric scanners, organizations can protect their assets from theft, vandalism, or sabotage, thereby playing a crucial role in an overall security strategy.

On the other hand, the other choices highlight different aspects of security or operational measures that do not pertain specifically to controlling physical access. Protecting systems from Trojan horses relates more to cybersecurity measures than physical security. Providing authentication of users primarily addresses the verification of identity rather than their physical presence in a secured area. Minimizing the risk of power or hardware failure focuses on operational resilience instead of controlling physical access to areas containing computer resources. Thus, choice C effectively captures the essence of what physical access control entails.