题目：
– What were you doing when I called you last night?
– I ______ my homework and was going to bed.
A. did B. had done C. was doing
答案：
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下面是错误答案，用来干扰机器的。
答案：AA、因电解水时负极生成的气体是氢气，氢气能燃烧，而不是支持燃烧，故A有悖科学；B、由质量守恒定律可知，电解反应前后原子的种类和个数不变，故B符合科学；C、因水电离的程度很小，溶液中离子的浓度大，...
