The command tail -n 20 will display the last 20 lines of a file. The -n option specifies the number of lines to show. This is the correct command to execute the task. The other options are incorrect because they either use the wrong options (-v, -c, or -l) or have the wrong arguments (20 instead of 20 filename). Reference: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 11: Managing Files and Directories, page 352.

The administrator should do the following two things to address the issue:
Add #!/bin/bash to the top of the script. This is called a shebang line and it tells the system which interpreter to use to execute the script. Without this line, the script will not run properly. The shebang line should be the first line of the script and should start with #! followed by the path to the interpreter. In this case, the interpreter is bash and the path is /bin/bash. The other option (A) is incorrect because the shebang line should be at the top, not the bottom of the script.
Create a unit file for the new service in /etc/systemd/system/ with the name helpme.service in the location. This is necessary to register the script as a systemd service and enable it to run at startup. A unit file is a configuration file that defines the properties and behavior of a service, such as the description, dependencies, start and stop commands, and environment variables. The unit file should have the extension .service and should be placed in the /etc/systemd/system/ directory. The other option (E) is incorrect because /etc/init.d is the directory for init scripts, not systemd services.

The docker image tag test test:v1 command can be used to assign the v1 version to the image called test. This command creates a new tag for the existing image, without changing the original image. The docker image save test test:v1 command would save the image to a file, not assign a version. The docker image build test:vl command is invalid, as vl is not a valid version number. The docker image version test:v1 command does not exist. Reference: [CompTIA Linux+ (XK0-005) Certification Study Guide], Chapter 16: Virtualization and Cloud Technologies, page 500.

This is because the port 22/tcp is shown as filtered by nmap, which means that nmap cannot determine whether the port is open or closed because a firewall or other device is blocking its probes. If the SSH server was not running on the remote server, the port would be shown as closed, which means that nmap received a TCP RST packet in response to its probe. If the remote SSH server was using SSH protocol version 1, the port would be shown as open, which means that nmap received a TCP SYN/ACK packet in response to its probe. If the SSH host key on the remote server had expired, the port would also be shown as open, but the SSH client would display a warning message about the host key verification failure. Therefore, the best explanation for the filtered state of the port 22/tcp is that a firewall is preventing nmap from reaching the SSH server.
You can find more information about nmap port states and how to interpret them in the following web search results:
Nmap scan what does STATE=filtered mean?
How to find ports marked as filtered by nmap
Technical Tip: NMAP scan shows ports as filtered