Explanation
The most likely cause of the servers displaying the wrong time is A. A firewall. A firewall is a network security device that monitors and controls incoming and outgoing network traffic based on predefined rules. A firewall can block or allow certain ports, protocols, or applications that are used for network communication.
One of the protocols that is used for time synchronization is the Network Time Protocol (NTP), which requires the use of UDP port 123 for all time synchronization1. If a firewall blocks this port, it can prevent the servers from obtaining the correct time from the time source. Therefore, the server administrator should check the firewall settings and make sure that UDP port 123 is allowed for NTP traffic.