Correct Answer : man
Explanation : UNIX provides us with a facility of man command, which is used for getting documentation of any command. For example, to seek help on wc command simply type man wc. This will simply display all the possible operations, options, description, synopsis of wc command. The POSIX specification requires only one available option with man command i.e. -k, which prints a one-line description of the command. whatis command is also available on many UNIX systems which also displays a one-line description of the command. man -f emulates the behavior of whatis command.
