通过shell执行一个命令，必须先敲入一个（）。
A.参数
B.命令
C.操作符
D.终端ID号
参考答案：B
Questions 11-14
A．He has a big family.
B． He has to work at home.
C．His mother-in-law likes to have parties.
D． His children are rather naughty.
