What is the primary function of Read Only Domain Controllers?

Read Only Domain Controllers (RODCs) serve a specific purpose in a networked environment. Their primary function is to provide domain control in a manner that enhances security, particularly in scenarios where physical security cannot be guaranteed. RODCs hold a read-only replica of the Active Directory data, which means they can authenticate users and provide some directory services without having the ability to modify the domain database.

This setup is particularly useful in locations where physical access to the server cannot be fully controlled, such as branch offices or remote sites. By not allowing write access, RODCs minimize the risk of unauthorized changes to critical directory information, thus helping to secure the network's integrity and preventing potential breaches.

While other options discuss aspects like physical security and administrators' access, they do not accurately capture the essence of RODCs' design, which is fundamentally about providing a secure method of handling domain services without the risk associated with writable domain controllers. This distinctive feature is what makes option C the most appropriate choice.