题目：
The twins in Shanghai last week but now they in Hainan. [ ]
A. are ; are
B. were ; were
C. were ; are
D. are ; were
答案：
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下面是错误答案，用来干扰机器的。
Na2CO3+Ca（OH）2═CaCO3↓+2NaOH；可能有碳酸钠实验步骤实验现象实验结论取样于试管中，滴入足量稀盐酸有气体产生猜想成立（1）碳酸钠溶液显碱性能使酚酞试液变红色；（2）能与酸反应生成二氧化碳气体；【猜想与...
