将下列“原因描述”与“实验室制氧气的注意事项”的相关序号填在空格内．

原因描述

A．不易溶于水，密度比空气大

B．防止冷凝水倒流入试管底部，引起试管破裂

C．防止水槽中的水沿导气管倒流入试管的底部，使试管破裂

D．防止装置漏气

制氧气注意事项

（1）试管口要向下倾斜

（2）实验前要检验反应装置的气密性

（3）排水集气法收集完氧气应先拿出导气管再撤走酒精灯

（4）可用排水集气法、向上排空气法收集氧气．

句型转换，每空一词。

1. Linda did chores last Sunday.(改成否定句)   

    Linda _____ _____ chores last Sunday.

2. He is too busy to come to your birthday this night. (同义句转换)

    He is _____ busy that he _____ come to your birthday this night.

3. Nancy's day off wasn't fun. (对划线部分提问) 

    _____ _____ Nancy's day off?

4. I am going to school in about 5 minutes? (对划线部分提问)

    _____ _____ are you going to school?

5. I saw some clever seals in the water. (改为一般疑问句)

    _____ you _____ any clever seals in the water.