在“验证力的平行四边形定则”的实验中，某小组利用如图所示的装置完成实验，橡皮条的一端C固定在木板上，用两只弹簧测力计橡皮条的另一端拉到某一确定的O点．

下列各句中，加线的成语使用恰当的一项是（    ）

任务型阅读。（5分）
Charles，Isabel，Alex，Tara和Toby五个人都爱好体育。现在他们正打算从事各自喜欢的项目。请仔细阅读第76--80题中的个人情况说明，然后选出符合各人要求的最佳选项。
【小题1】Charles works in the city center and wants to take up a sport that he can often do during his lunch break. He enjoys a game in which he can play with his workmate on the desk to relax.
【小题2】 Isabel, aged 17, is a Chinese girl who studies in the US now.  She never misses any matches played by Houston Rockets.  She hopes to follow in Yao Ming’s steps.
【小题3】Alex likes water sports very much.  He is good at showing different styles, such as butterflies, frogs and so on. Believe it or not, he can dive under water for 2. 5 minutes.
【小题4】Tara comes from America. Now she teaches English in a middle school in Beijing.  In her free time, she would like to go in for a traditional sport so that she can learn more about China.
【小题5】 Toby is a student in charge of PE lesson in Riverside Middle School. These days he is training hard for the coming sport meet. He wants very much to break the school record of 175cm.
    
A                B               C               D             E

计算|﹣2|+（ $\frac{1}{3}$ ）^﹣1×（π﹣ $\sqrt{2}$ ）²﹣ $\sqrt{9^2+{\left(-1\right)}^2}$ =____．

下列家庭小实验中，主要发生物理变化的是（   ）