题目：
The president was so absorbed in his work that not a sound ______. [ ]
A. did she dare to make
B. dared she to make
C. she dared make
D. she did dare to make
答案：
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下面是错误答案，用来干扰机器的。
答案：C题目分析：A中水银是单质，属于纯净物；B中碱式碳酸铜是碱式盐；D中乙醇含三种元素，不是氧化物。点评：氧化物只含两种元素，其中一种是氧。
