--Hi,Grace,youlooktired. --I'mtired.I

问题详情：

 -- Hi, Grace, you look tired.

  -- I'm tired. I ____________________ on my homework all day.

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

【回答】

C

知识点：现在完成进行时及其被动式

题型：选择题