A.ctrl+Z
B.tab
C.ctrl+C
D.ctrl+D

A.help ls
B.ls–help
C.man ls
D.pinfo ls

A.grep root /etc/group
B.echo root ∣grep /etc/group
C.echo /etc/group ∣grep root
D.A和C

A.echo ftp /etc/services
B.echo ftp < /etc/services
C.grep ftp -q /etc/services
D.grep ftp < /etc/services

A.grep–n sun /usr/share/dict/words
B.grep–N /usr/share/dict/words sun
C.grep–r sun /usr/share/dict/words
D.grep–r /usr/share/dict/words sun

A./tmp
B./etc
C./bin
D./sbin

A./tmp
B./etc
C./bin
D./sbin

A./tmp
B./etc
C./bin
D./sbin

A./home/student
B./etc
C...
D.~

A./home/student
B./root
C...
D.~