关于物理学思想方法，下列说法中，正确的是 [ ]

A．著名的伽利略斜面实验，主要应用了控制变量方法

B．在研究加速度a和外力F，质量m的关系时，主要应用了等效替代的方法

C．在研究气体的温度不变时，压强与体积的关系时，主要应用了理想实验方法

D．在定义“速度”、“加速度”、“电场强度”等物理量时，主要应用了比值的方法

用所给单词的正确形式填空。

1. The joke is _______ (fun). We all laugh.

2. Where is the _______ (happy)? It's in your own hands.

3. My mother was _______ (satisfy) with what I did.

4. Don't let him _______ (go) there alone.

5. Have you finished _______ (read) the book?

6. All the students are busy _______ (clean) the room.

7. Did you hear the baby _______ (cry) in the next room?

8. Jack went to school without _______ (take) his backpack.