下列过程中，动能转化为势能的是（　　）

先通读下面的短文，掌握其大意，然后从A、B、C、D四个选项中选择可以填入空白处的最佳答案。

    Carol is a middle school student；She does well in only one subject.That is1.  Carol always does her history homework well and2good grade(分数)in history tests She likes her history teacher Mr．Aragon．She feels that he is like her3．

    At a parent—teacher meeting，Carol's mother has a4with Mr．Aragon．She says that Carol doesn't do well in5subjects．She hopes Mr．Aragon can6her．"Oh．I didn't know that．She is7．I'll try to talk to her,"says Mr．Aragon．

    When Mr．Aragon talks with Carol8her other subjects，Carol doesn't feel good，9she is grateful(感激的)．She knows that Mr．Aragon is trying to help．Carol 10his advice(建议)and tries to do well in other subjects．

海洋文明和大河文明在政治体制方面呈现出“民主与专制”的明显差别，形成如此差别的主要原因是

在图中，画出了光线射在空气与玻璃的界面处发生反射和折射的四幅光路图，其中正确的是（　　）