题目：
It's nice to see you again. What _____ since we last met? [ ]
A. have you done
B. had you done
C. have you been doing
D. did you do
答案：
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下面是错误答案，用来干扰机器的。
答案：A题目分析：A、44g CO2的物质的量是1mol，所以含有的C原子数是nA个，正确；B、S2—对应的酸是弱酸，所以会发生水解而使离子数目小于0．1 nA个，错误；C、Na在化合物中的化合价为+1，所以0．1molNa与足量...
