问题
选择题
镁粉在焰火、闪光粉、鞭炮中是不可少的原料，工业上制造镁粉是将镁蒸气在某种气体中冷却．现有下列气体：①空气、②CO2、③Ar、④H2、⑤N2，其中可作为冷却气体的是（ ）
A．①和②
B．②和③
C．③和④
D．④和⑤
答案
答案：C
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镁粉在焰火、闪光粉、鞭炮中是不可少的原料，工业上制造镁粉是将镁蒸气在某种气体中冷却．现有下列气体：①空气、②CO2、③Ar、④H2、⑤N2，其中可作为冷却气体的是（ ）
A．①和②
B．②和③
C．③和④
D．④和⑤
答案：C
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| I have a happy family. Do you have 1 , too? There are five 2 in my family. 3 my grandfather, my grandmother, my parents and I. My grandfather and my grandmother are old, so they 4 every day. They cook meals and wash 5 every day. My father is a 6 . He is in the People's Hospital. My mother works there, 7 . She works hard. Both of them are busy. I study at No. 6 Middle School. I work hard 8 school. I 9 in my school. I go home 10 Saturday. | ||||
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