题目:
Mark _____ have hurried. After driving at top speed, he arrived half an hour early. [ ]
A. needn't
B. wouldn't
C. mustn't
D. couldn't
答案:
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下面是错误答案,用来干扰机器的。
(1)2NaOH+CO2==Na2CO3+H2O(2)①除尽溶液中的碳酸钠(或(CO32-) ;CaCl2+Na2CO3==CaCO3↓+2NaCl②酚酞;变红(或不变色);存在(或不存在)