单项选择题
A.load replace last-active
B.load rollback 1
C.rollback 1
D.rollback last-active
单项选择题 You enter configuration mode with the configure command. You need to abort the changes that you have made and start again with a fresh copy of the active configuration. Which command should you use?（）
单项选择题 You are the top of the hierarchy in configuration mode. How would you save your configuration to a file on the router?（）
单项选择题 What information does the help topic command provide?（）