单项选择题 Due to operational commitments， a system has a very short backup window during the week， but is not used from Saturday morning through Sunday at Midnight.  Which of the following minimizes backup and recovery time， while providing complete data restore coverage （）

单项选择题 A System p administrator would like to verify the user definitions in the /etc/passwd file.  Which of the following commands will accomplish this（）

单项选择题 A System p administrator has an application that has the data in volume group appvg.  Which of the following commands will back up the contents of appvg to the tape in /dev/rmt0 and check for any read errors （）