某校历史兴趣小组在学习《近代中国历史进程概说》时，根据书中“近代中国社会的发展轨迹像个元宝形，开始是下降，降到谷底，然后上升，升出一片光明……”的描述，绘制了下图。请结合该图，回答问题。

常见的自然现象，能用分子运动知识解释的是（　　）

（Ⅰ）当实数m取什么值时，复数z是纯虚数；

（Ⅱ）当m=0时，化简 $\frac{z^2}{z+5+2i}$ ．

    One day, in New York, the employees of a big company returned from their lunch break and were greeted with a sign on the front door. The sign said, “Yesterday the person who had been hindering (阻碍) your1in this company passed away. We2you to join the funeral in the room that has been3in the gym.”

    At first, all the employees were sad to4that one of their colleagues had died,5after a while they started getting6about who this person might be.

    The excitement 7 as the employees arrived at the gym to pay their last 8. Everyone wondered, “Who is this person that was hindering my growth? Well,9he's no longer here!”

    One by one the10got closer to the coffin and when they looked inside it, they11became speechless. They stood over the coffin,12 into silence, as if someone had 13 the deepest part of their soul.

    There was a mirror inside the coffin — everyone who looked inside it could see himself. There was also a 14 next to the mirror,15“There is only one person who is capable to set16 to your growth: it is YOU.”

    You are the only person who can revolutionize (变革) your 17. You are the only person who can 18 your happiness, realization and success. You are the only person who can help yourself. Your life does not change when others change. Your life changes when you change, when you go 19 your limiting beliefs and when you realize that you are the only one 20 for your life.

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      太阳花一种极普通的花。我喜欢太阳花，它是夏天里常见的花。太阳花的茎有红色的，有绿色的。那茎很嫩，似乎用手一掐，就会冒出水来。 太阳花的叶子很特别小而厚。叶子的表面像涂了一层薄薄的蜡，光而细腻（nì）。

      花朵并不大，多层的花瓣自然娇艳，单层的花瓣更俏（qiào）丽，真讨人喜欢。

      我喜欢太阳花，不只在于它颜色鲜艳，更因为它有强的生命力。它不怕日晒、风吹、雨打， 那样子总是蓬（péng）蓬勃（bó）勃。只要掐一根小小的茎，插在泥土了，不久就会生根开花。