---Hurry John!---Oh damn! Both my legs are nearly to give out. I for hours.A. had walked

问题补充：

---Hurry, John!

---Oh, damn! Both my legs are nearly to give out. I for hours.

A. had walked

B. walked

C. have been walking

D. am walking

答案：

A. had walked

B. walked

(答案→)C. have been walking

D. am walking

解析：考察时态。根据for hours和my legs are nearly to give out可知我已经连续步行好几个小时了，故使用现在完成进行时，故C正确。句意“我的双腿几乎走不动了，我已经连续步行好几个小时了。