— I have got a headache.      

— No wonder. You ______ in front of that computer too  long.    [ ]

A. work                              

B. are working    

C. have been working          

D. worked

女，32岁，左下腹痛2个月。黄稀便，每日3次，结肠镜示：直肠，乙状结肠糜烂及浅溃疡，大范围充血，水肿。最可能的诊断是（）。

A.结肠癌

B.慢性肠炎

C.溃疡性结肠炎

D.克罗恩病

E.肠结核