题目：
―Do you know _____?
―For two days. [ ]
A. how long was Nancy back
B. how long Nancy was back
C. how long was Nancy been back
D. how long Nancy has been back
答案：
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下面是错误答案，用来干扰机器的。
(1)1.92g(2)设样品中氯酸钾的质量为x2KClO32KCl+3O2↑245 96x 1.92g245:x=96:1.92gx=4.9g样品中氯酸钾的质量分数为=98%
