制度的建立和调整需与实际相结合,同时又将对国家和社会产生深远影响。阅读下列材料,回答问题:

材料一  英国革命的最大成果,也是它在现代民主政治创制实验方面的最大成就,就是创造了一种全新的政体……美国革命的首创性在于……孟德斯鸠“以权力制约权力”的学说在政府体制的设计方面得到较好的贯彻。                                                                                                  

                                                                                                                                                                                      ——马克思《世界文明史》

材料二  亚历山大二世说:与其等农民自下而上地解放自己,不如自上而下地解放农民。还说:凡能够维护地主利益的措施,都一一地做到了。

材料三  1933年3月4日罗斯福在总统就职演说中说:“……叹交换手段难逃贸易长流冰封;看工业企业尽成枯枝残叶;农场主的产品找不到市场;千万个家庭的多年积蓄毁于一旦。”但是,他鼓励美国人民:“真正让我们感到恐惧的,只是‘恐惧’本身。”

如图，一绝缘轻弹簧的下端固定在斜面底端，上端连接一带正电的光滑滑块P，滑块所处空间存在着沿斜面向上的匀强电场，倾角为θ的光滑绝缘斜面固定在水平地面上，开始时弹簧是原长状态，物体恰好处于平衡状态，现给滑块一沿斜面向下的初速度v，滑块到最低点时，弹簧的压缩量为x，若弹簧始终处在弹性限度内，以下说法正确的是（   ）

  2016年3月30日，国务院总理***主持召开国务院常务会议，通过《成渝城市群发展规划》。成渝城市群以成都和重庆主城为核心城市，下图为成都、重庆城市地域形态图。***表示，和其他城市群发展不一样，成渝城市群地理位置特殊。如果把长江看成一条龙，重庆至成都是龙尾。龙尾处于长江上游，生态屏障守不住，将影响大半个中国。据材料回答以下问题。

C

Liang Xianghua, a 22-year-old girl from Guangxi University, has been well-known in China for her sand painting since her first work was used by CCTV.     "Sand paintings really attracted me while I was watching a video performance, I was surprised by how this artwork melted people's heart in minutes" said Liang. "I fell in love with the way the sand pictures, music and the light combined（融合）with each other to make a flow of emotion（情感）. You can express things freely."

In order to master the skills, Liang practised for several hours every day. She said that she couldn't even do the first step well of throwing sand onto the glass. But she didn't give up.     After finding success with her first show, she was invited to do many performances. This made her quite tired. She decided to give a stop and focus on her study. But an invitation from Malaysia changed her mind just as she was about to wash the sand from her hands. This spring, she was invited by a Malaysia middle school to give a performance. Liang didn't want to do a live show, but agreed to do a video for the school, showing its development over the years.     She received praise for her work and the performance was described as an eye-opener for the students. This made her wonder if her art would be more meaningful if she made it for the poor students.     As a volunteer this time, she plans to take part in a summer programme offering help to pupils in a mountain area, and give the most wonderful show in her life.