单项选择题 An operator is asked to rewind and eject a tape from a system. Which command will accomplish this without touching the tape drive?（）

单项选择题 When an operator is trying to log off the system displays this message: you have running jobs?? What does this mean?（）

单项选择题 An application owner wants to grant write permission to all users for all the files and directories in the application directory. Which of the following is the correct command?（）