Which of the following commands will display the last 30 lines of /var/log/bigd.log as well as new content as it is appended to the file by another process?

cut is a text-processing command used to extract fields or columns from lines; it has no capability to display lines from the end of a file or follow new content.

head displays the first lines of a file, not the last, and does not support following appended content; this option also contains garbled syntax.

tail -f tells the command to follow the file and print new data as it is appended by other processes, which is the standard way to monitor live log files. The -n 30 option sets the initial output to the last 30 lines, satisfying both requirements in the question. The path /var/log/bigd.log is correctly specified with the proper case.

tac outputs a file in reverse line order and does not support following live appended content.

cat does not accept -r or a numeric -n argument for limiting output to a trailing number of lines, and it does not follow file changes.