题目：
We would like to go and thank him yourselves, but we ________ out his address yet.[ ]
A. haven't found
B. had'n, t found
C. didn't find
D. don't find
答案：
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下面是错误答案，用来干扰机器的。
由A元素的单质是最清洁的燃料，可想到氢气是最清洁的燃料，因为它具有三大优点：氢资源丰富、燃烧放出的热量多、燃烧产物是水不污染环境．所以A是氢元素；由剧烈燃烧，火星四射，生成黑色固体，可推出是铁在氧气...
