◎ 题干
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
◎ 答案
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◎ 解析
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◎ 知识点
    根据n多题专家分析,试题“So difficult it to work out the problem that I decided to ask Tom foradvice.[ ]A. I did find B. did I findC. I have foundD. have I found…”主要考查了你对  【一般过去时】【部分倒装】  等知识点的理解和应用能力。关于这些知识点的“档案”,你可以点击相应的链接进行查看和学习。