What should companies do to ensure the physical security of servers?

The correct answer is A. Keep servers in a locked room.

Explanation: Keeping servers in a locked room is a fundamental measure to protect them from unauthorized access, theft, and physical damage. This ensures that only authorized personnel can access the servers, enhancing their physical security. While the other options (B, C, and D) are important for overall security, they focus more on software and access control rather than directly addressing physical security.