What application can be used in place of xhost？ Please enter only the name without path. Answer：（）

单项选择题WhatisthedifferencebetweenthE.removeandthE.purgeactionwiththedpkgcommand？（）

A. -remove removes the program， -purge also removes the config files
B. -remove only removes the program， -purge only removes the config files
C. -remove removes a package， -purge also removes all packages dependent on it
D. -remove removes only the package file itself， -purge removes all files related to the package

单项选择题Thecommandecho$!willproducewhatoutput？（）

A. the process id of last background command
B. the exit status of the last command
C. the exit status of the last background command
D. the process id of the current shell
E. the name of the command being executed

填空题Whatcommandwithalloptionsand orparameterwillsendthesignalUSR1toanyexecutingprocessofprogramapache2？（）

填空题Whichcommand（withoutoptions）wouldyouusetodisplayhowmuchspaceisavailableonallmountedpartitions？（）

单项选择题WithXorg7.0，whatisthenameofthedefaultfontserver？（）

A. xfserv
B. xfs
C. fonts
D. xfstt
E. fserv