If a computer crashes you will lose the file you on unless you save it regularly.A. are

问题补充：

If a computer crashes,you will lose the file you on unless you save it regularly.

A. are working

B. work

C. will work

D. worked

答案：

A. are working

B. work

C. will work

D. worked

解析：考查时态。依据常识可以知道，电脑瘫痪，之前的文件不会丢失，而即将进行的文件也不可能丢失，所以可以排除C、D两项；再依据后文的save it regularly可知，这些文件应该是正在进行的文件，所以用进行时态。