Eddie has lived here _____________four years ago.

A．before

B．after

C．when

D．since

查看/home/abc.txt文件的前20行内容所用到的命令是（）。

A.more-20/home/abC.txt

B.less-20/home/abC.txt

C.head-20/home/abtxt

D.ls-20/home/abC.txt