用括号内所给单词的适当形式填空，使句意完整。

1. I have a brother and a sister. So my parents have three _______(child).

2. Can you help me with _______(swim)?

3. I can speak a little _______(China).

4. Jack's father and mother are _______(music).

5. He doesn't play _______(sport).

6. Please come and join _______(we).

7. She wants _______(play) volleyball with me.

8. He can play the drums, but I can't play _______(it).

9. Does your mother like_______(dance)?

10. The _______(one) day of the week is Sunday.

张华同学取两张相同的16K白纸，探究影响纸片下落的快慢的因素．张华将一张纸对折一次，另一张纸对折三次，从同一高度同时释放两张纸．

（1）张华控制的变量有______．

（2）张华研究的是变量______对纸片下落快慢的影响．

（3）实验过程中，张华用到的测量工具是______．

（4）张华比较纸片下落快慢的方法是______．