Multiple choice technology operating systems Which of the following would return the process ID of the sleep command? test sleep 1 sleep 1 && echo $0 sleep 1 & echo $! sleep 1 & echo $$ Reveal answer Fill a bubble to check yourself C Correct answer Explanation In shell, $! returns the PID of the last background process. Option C correctly backgrounds sleep with & then echoes $!. Option D's $$ is the current shell's PID, and $0 in B is the shell name, not the background process.