Final answer:
Proximity authentication access control is the most fitting solution to enforce a company policy that restricts smartphone use to the company campus by identifying and tracking all cell phones within a certain area.
Step-by-step explanation:
To enforce a company policy that smartphones may not be used off of the company campus, the ideal technological solution would be c. Proximity authentication access control. This method identifies and tracks all cell phones that attempt to connect to the company's network and ensures that devices cannot be used outside a certain geographical area. This solution aligns with the necessity to balance privacy concerns and security, much like the dilemmas presented by tools enabled under acts like the US Patriot Act. Given that surveillance tools can be beneficial for security but require careful regulation and oversight, proximity authentication is a responsible way to enforce company policy without overly invasive measures.