Since you are in the preliminary stages of your project, you estimate that your project will most probably last 1 year-however, optimistic scenario is that it will get over within 6 months and pessimistic scenario is 18 months. This kind of estimate is also called ______ .

A) definitive
B) capital cost
C) order of magnitude
D) feasibility

进行文件复制的基本方法是

A．选源文件，复制；选目标文件夹，粘贴
B．选目标文件夹，复制；选源文件，粘贴
C．选源文件，粘贴；选目标文件夹，复制
D．选源文件，复制；选目标文件夹，双击
E．选目标文件夹，剪切；选源文件，粘贴