单项选择题
A. The contents of the file foobar.
B. Hello
C. No output but a file named foobar is created.
D. Hello foobar
E. Hello foobar foobar
单项选择题 WhichsystemadministrationcommandyoucanusetoupdateId.so.cacheaftertheinstallationofnewsharedlibraries？（）
单项选择题 YouarerunningLinux2.0.36andyouneedtoaddaUSBmousetoyoursystem.Whichofthefollowingstatementsistrue？（）
单项选择题 Whichofthefollowingcommandsmakes/bin/fooexecutablebyeveryonebutwritableonlybyitsowner？（）