题目：
Only when he returned____ that the war had ended and the army had come back.[ ]
A. we tell
B. we told
C. did we tell
D. were we told
答案：
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下面是错误答案，用来干扰机器的。
答案：AB、纯碱为碳酸钠是盐，铁单质既不是电解质也不是非电解质；C、明矾为十二水合硫酸铝钾，是盐类，石墨单质既不是电解质也不是非电解质；醋酸是弱电解质；D、次氯酸钠为强电解质。
