A differential backup is a type of backup that copies all the files that have changed since the last full backup. A differential backup requires more storage space than an incremental backup, which only copies the files that have changed since the last backup of any type, but it also requires less time to restore in case of data loss. By combining a full, weekly backup with daily differential backups, the administrator can ensure that only two backup sets are needed to restore a full backup as quickly as possible. Verified Reference: [Incremental vs Differential Backup]

Explanation
The administrator should use the command chmod 754 /home/Ann to resolve the issue without granting unnecessary permissions. The chmod command is used to change the permissions of files and directories on a Linux server. The permissions are represented by three numbers, each ranging from 0 to 7, that correspond to the read , write (w), and execute (x) permissions for the owner, group, and others respectively. The numbers are calculated by adding up the values of each permission: r = 4, w = 2, x = 1. For example, 7 means rwx (4 +
2 + 1), 6 means rw- (4 + 2), 5 means r-x (4 + 1), etc. In this case, Ann's home directory has the permissions dr-xr-xr-, which means that only the owner (d) can read and execute (x) the directory, and the group and others can only read and execute (x) but not write (w) to it. This prevents Ann from saving files to her home directory. To fix this issue, the administrator should grant write permission to the owner by using chmod 754
/home/Ann, which means that the owner can read , write (w), and execute (x) the directory, the group can read and execute (x) but not write (w) to it, and others can only read but not write (w) or execute (x) it.
This way, Ann can save files to her home directory without giving unnecessary permissions to others.

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.

The tool that the administrator should use to check for unnecessary running services across 12 servers is a port scanner. A port scanner is a tool that scans a network device for open ports and identifies the services or applications that are running on those ports. A port scanner can help detect any unauthorized or unwanted services that may pose a security risk or consume network resources. A port scanner can also help troubleshoot network connectivity issues or verify firewall rules.
Reference: https://www.getsafeonline.org/business/articles/unnecessary-services/