So difficult it to work out the problem that I decided to ask Tom for advice.
A. I did find
B. did I find
C. I have found
D. have I found
网友回答
A. I did find
(答案→)B. did I find
C. I have found
D. have I found
解析：句意：发现解决这个问题如此困难，所以我答应向汤姆咨询一下。So位于句首，应使用部分倒装。另外本句用过去时态。