单个无连续选择文件时可用鼠标和（）键组合选中。
A、Shift
B、Alt
C、Ctrl
D、Tab
参考答案：C
You will find what great benefit the computer you own can be________each time you use it to help you
work.[ ]
A. for
B. at
C. on
D. of
皮下注射法
