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：句子使用的基本句式为so…that…结构。按英语语法，当该结构的so…置于句首时，其后的句子(主句)要用倒装语序，如：So loudly did he speak that even people in the next room could hear him. 他讲话声音那么大，隔壁屋里的人都听得见。