$1 is a positional paramater. $0 is the name of the script itself, $1 is the first argument, $2 the second, $3 the third, and so forth. In this example, the value of $0 is "./add-user.sh", the value of $1 is "tom", the value of $2 is "richard" and the value of $3 is "harry".

Both "netstat -l" and "ss -l" show listening sockets. However, the replacement for the netstat command is "ss" and is the currently preferred command.

The "/etc/passwd" file contains many pieces of information including the UID (User ID number) for every local user on the system. The other options are invalid.

The correct answer is "lscpu" as it displays information about the CPU architecture. The other options do not provide the CPU architecture information.

Per the FHS, the "/mnt" directory is to be used for temporarily mounting filesystems, making it the correct answer. The "/export" directory was typically used to share NFS shares on Solaris. The "/tmp" directory is use by programs to store temporary files and is not typically used for manual mount points. "/var" is used for variable data, and "/var/umount" is not a standard directory. Although any directory can be used as a mount point, it is best to follow the FHS.

"getsebool ssh_sysadm_login" displays the value for the ssh_sysadm_login SELinux boolean. The "getsebool" command requires an argument, making just "getsebool" incorrect. "setsebool ssh_sysadm_login=on" actually modifies the value instead of just displaying it.

The EFI system partition, also known as ESP, is an OS-independent partition that stores the EFI bootloaders, applications and drivers to be launched by UEFI firmware. It is mandatory for UEFI booting. It is typically mounted at "/boot/efi". The "/boot" directory contains other components, such as the Linux kernel itself. "/root/efi" is not used because "/root" is the root account's home directory. "/dev/efi" does not exist.

The only valid I/O scheduler listed is "mq-deadline", making it the correct answer.

The correct answer is "route add -net 10.11.12.0 netmask 255.255.255.0 gw 10.11.12.1". The other options do not add a route.

The "nmcli" command-line tool can be used to control NetworkManager, making it the correct answer. The other commands are invalid.