如图示，先拨动张紧的细橡皮筋，再拨动粗橡皮筋，观察先后两次发声时橡皮筋振动快慢及声音的特点，记录如下表：

实验2如图所示，两次敲打音叉，观察泡沫球被弹起，第一次轻敲音叉，发现泡沫球被弹起的高度较小：第二次重敲音叉，发现泡沫球被弹起的高度较大，而且音叉前后两次发出的声音是前者较小后者较大。

分析以上实验，回答下列问题：

阅读下面短文，按要求完成各项任务。

    I went through some difficult times, dealing with the pressures of growing up. I found it hard to communicate with my mother. Relations between us became difficult.

    One day, I ran away from home and stayed away for many hours. When I returned home at night, I saw all the pain, anger and disappointment on my mother’s face. ①      . We agreed to have breakfast together the next morning. It was a turning point in both of our lives and our relationship.

We decided to go to a restaurant. On our way to the table I noticed my mother had two notebooks. I asked her what they were for. She explained to me that sometimes it was easier to write down our feelings rather than talk about (A) them. We would write down our feelings in the form of a letter. It could be as long or as short as we wanted.

    Our first topic was “Why I'm so angry?” I wrote a half page, and my mom filled up nearly three pages. (B) I watched tears run down her face as she wrote. I never realized anyone could hide so much anger. After we finished writing, we exchanged our notebooks. As soon as I started reading my mother's words, I began to cry and so did she. When we finished reading, we discussed our feelings. ②      . Our talk helped me realize so many things I had never thought of before, not only about my mother but also about other people.

     My mother and I continue to use our notebooks as a way of communicating our anger and worries, and our happiness as well. We know that no matter how we feel about each other, our notebooks are a safe place to express our feelings. We have come to an agreement that at the end of each letter we write, “I love you.”