多项选择题
A. rollback
B. delete
C. delete 0
D. rollback 0
单项选择题 What must you type to enter operational mode from the root@% command prompt?（）
单项选择题 When using keyboard shortcuts, which keystroke combination allows users to erase a single word to the left of the cursor?（）
单项选择题 When using keyboard shortcuts, which single keystroke combination allows users to erase the entire current command?（）