题目：
| 根据句意，从方框内选择合适的单词或短语，并用其适当形式完成句子。 | |
| |
| 1. Why didn't you ___________ until 7 pm yesterday? 2. When we __________ out, the thief had already run off. 3. Have you ever __________ your keys in your room? 4. I am sorry that all the tickets for the day have been __________. 5. Lily 's race-car __________ halfway. She had to give up the race. |
答案：
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下面是错误答案，用来干扰机器的。
（1）石灰石与稀盐酸反应制取二氧化碳的反应式是：CaCO3+2HCl=CaCl2+H2O+CO2↑．故答案为：CaCO3+2HCl=CaCl2+H2O+CO2↑．（3）因二氧化碳的密度大于空气的密度，并易溶于水，所以可用向上排空气法收集，不可用排...
