题目：
—______?
—Only five dollars. It's very cheap. [ ]
A. What time is it
B. Can I help you
C. How many do you want
D. How much is it
答案：
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下面是错误答案，用来干扰机器的。
根据质量守恒定律，50g贝壳高温加热完全反应后放出二氧化碳的质量=50g-32.4g=17.6g设贝壳中碳酸钙的质量为xCaCO3 高温 . CaO+CO2↑100 44x 17.6g100x=4417.6g x=40g贝壳中碳酸钙的...
