The best way to protect an organization against social engineering is to provide recurring training and support.
Social engineering is a type of attack that exploits human psychology and behavior to manipulate people into divulging confidential information or performing malicious actions. Social engineering can take various forms, such as phishing emails, phone calls, impersonation, baiting, or quid pro quo. The best defense against social engineering is to educate and empower the employees to recognize and avoid common social engineering techniques and report any suspicious activities or incidents. Recurring training and support can help raise awareness and reinforce best practices among the employees.

RAID (Redundant Array of Independent Disks) is a technology that combines multiple hard drives into a logical unit that provides improved performance, reliability, or capacity. RAID can be implemented by hardware, software, or a combination of both. Hardware RAID uses a dedicated controller to manage the RAID array, while software RAID uses the operating system or a driver to do the same1.
In this scenario, the technician noted that the RAID hard drives were functional while troubleshooting a motherboard failure. This means that the data on the drives was not corrupted or lost. However, the technician installed a spare motherboard with similar specifications and used the original components. This means that the new motherboard may not have the same RAID configuration as the old one, or it may not recognize the existing RAID array at all. Therefore, the technician needs to reconfigure the RAID in order to restore operations with minimal downtime.

The df -h command should be used to identify the issue of not being able to save large files to a directory on a Linux server. The df -h command displays disk space usage in human-readable format for all mounted file systems on the server. It shows the total size, used space, available space, percentage of use, and mount point of each file system. By using this command, a technician can check if there is enough free space on the file system where the directory is located or if it has reached its capacity limit.

This is the most likely misconfigured setting because DNS is the service that resolves hostnames to IP addresses and vice versa. If the DNS server is incorrect or unreachable, the administrator will not be able to log on to the server with a domain account because the server will not be able to authenticate with the domain controller. References:
https://docs.microsoft.com/en-us/troubleshoot/windows-server/networking/dns-troubleshooting

An emergency change request is a type of change request that is initiated in response to an urgent situation, such as a system breach, that requires immediate action to restore normal operations or prevent further damage. An emergency change request may bypass some of the normal change management procedures, such as approval, testing, or documentation, in order to expedite the implementation of the change. However, an emergency change request should still follow the basic steps of change management, such as identification, analysis, planning, execution, and evaluation, and should be reviewed and documented after the change is completed.
References: CompTIA Server+ Study Guide, Chapter 11: Change Management, page 443.