3. Explain briefly why one should not log in as the "root" user. 4. a) List three commands which allow one to obtain informa- tion. b) What is a shell? c) List three shells used in GNU/Linux. d) How does one know in which directory one is working in? How does one move to the parent directory? e) Give three commands which can show the contents of a file on the monitor. 5. a) What is a directory? b) List the six file types with their symbol in a 'ls -l' listing. c) State the two major types of partitions on a GNU/Linux system and state their function