写出下列化学反应的化学方程式（1）白磷燃烧：_______________ （

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问题填空题

写出下列化学反应的化学方程式

（1）白磷燃烧：_______________

（2）铁与硫酸铜反应：________________________．

答案

（1）4P+5O₂2P₂O₅；

（2）Fe+CuSO₄=FeSO₄+Cu．

单项选择题

关系数据库中，实现实体之间的联系是通过表与表之间的

A．公共索引

B．公共存储

C．公共元组

D．公共属性

补全对话，情景问答

补全对话.

A: Do you have a pen pal?

B: Yes, I do. I have a boy pen pal. He's Pete.

A: ___1___?

B: He comes from Toronto, Canada.

A: ___2___?

B: He's tall with medium build, curly hair and blue eyes. Here is a photo of him.

A: ___3___?

B: He loves sports shows. Sports are his favorite.

A: ___4___?

B: Yes, I do. I want to go to Toronto and visit him next vacation.

A: ___5___?

B: It's warm in spring and not hot in summer. The weather is nice.

A: OK, I hope you have a good trip!

B: Thank you.