① 求电源电压U。

② 求通过电阻R₂ 的电流I₂。

③ 现用电阻R₀替换电阻R₁、 R₂中的一个，替换前后，只有一个电流表的示数发生了变化，且电流增大了0.1安。请判断被替换的电阻，并求出电阻R₀的阻值。

阅读理解
   The best thing about going to school is learning how to read. Books are great friends. They can help you to learn about anything you want to know. They can go anywhere with you. You can read about animals, faraway places, people, and anything else.
   Books are written by people called authors(作者). Authors think of things they want to write about. They make a plan for a book and start to write .Some authors write books that give us information(信息)and teach us things. Authors are very important people because they help us learn. Find a good book to read and read every day ,You will enjoy your time with a good book.

固定的倾角为37°的光滑斜面，长度为L=1m，斜面顶端放置可视为质点的小物体，质量为0.5kg，如图所示，当水平恒力较小时，物体可以沿斜面下滑，到达斜面底端时撤去水平恒力，物体在水平地面上滑行的距离为s，忽略物体转弯时的能量损失，研究发现s与F之间的关系如图所示，已知g=10m/s²，sin37°=0.6，cos37°=0.8．求：

下列属于合理发泄消极情绪的是（     ）