—Whyhaven’tyoufinishedyourhomeworkyet?  —Theproblemare...

问题详情：

 —Why haven’t you finished your homework yet ?

   —The problem are so difficult. I ______ hard without stop all day.

A. have been working     B. worked       C. have worked     D. work

【回答】

A

知识点：动词时态与语态

题型：选择题