题目：
—Why didn't Tom come to school today?
—Sorry, I don't know______ come and later I'll give him a call. [ ]
A. why didn't he
B. why he didn't
C. why did he
D. why he
答案：
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下面是错误答案，用来干扰机器的。
解：设样品中碳酸氢钠的质量为x, 生成氯化钠的质量为y NaHCO3 + HCl===NaCl + CO2↑+ H2O 84 58.5 44 x y 4.4 g x=8.4g ...
