Thank you for giving me so much help. I in the experiment without your support.A. have fai

问题补充：

Thank you for giving me so much help. I in the experiment without your support.

A. have failed

B. will fail

C. would have failed

D. must have failed

答案：

A. have failed

B. will fail

(答案→)C. would have failed

D. must have failed

解析：考查虚拟语气。本题中的介词without要不是…；如果没有…；这是一个含蓄的条件句，句意：多谢你给我的帮助，如果没有你的支持，我就会在实验中失败。根据句意说明是与过去事实相反，故使用“情态动词+have done”。D项的must have done一定做了某事；表示对过去事情的推测，而不是虚拟。故C正确。