A、PPP
B、L2TP
C、SLIP
D、PPTP
E、TFTP

A、route print
B、route show
C、route view
D、route display

A、POP3
B、IMAP
C、SMTP
D、S/MIME

A、echo The current working path is $PWD.
B、echo "The current working path is $PWD." Echo hello
C、echo 'The current working path is $PWD.' Echo hello
D、echo "The current working path is `pwd`."
E、echo The current working path is $PWD. Echo hello

A、date>>/tmp/date
B、date>/tmp/date
C、date 2>/tmp/date
D、date &>/tmp/date

A、5
B、7
C、9
D、10

A、mkdir /tmp/file
B、make /tmp/file
C、touch /tmp/file
D、mv /tmp/file

A、–i
B、–f
C、–b
D、–u

A、mv /tmp/test/oldfile newfile
B、mv /tmp/test/oldfile /tmp/test/newfile
C、mv oldfile /tmp/test/
D、mv oldfile newfile

A、ls -i /tmp
B、ls -l /tmp
C、ls -r /tmp
D、ls -d /tmp