下图为我国季风区某山地的地质横剖面示意图，该地区裁弯取直开挖了引水隧洞，连接了同一条河流的不同河段。读图完成下列各题。

重大的社会变革和历史进步，往往以思想解放为前提。阅读下列材料，回答问题。

材料一　是书何以作？曰为以夷攻夷而作，为以夷款夷而作，为师夷长技以制夷而作。

材料二　他以译述赫胥黎的《天演论》而在中国近代思想界名声显赫，是中国近代维新派的代表人物；他以进化论为武器，唤醒人们“自强保种”，挽救民族危亡；他被***主席评为“代表了全***出世以前向西方寻找真理的一派人物”(***《论人民民主专政》)，与洪秀全、康有为、孙中山齐名。

宇宙中有这样一种三星系统，系统由两个质量为m的小星体和一个质量为M的大星体组成，两个小星体围绕大星体在同一圆形轨道上运行，轨道半径为r．关于该三星系统的说法中正确的是（   ）

Dear God,

    Now that I am no longer young. I have friends whose mothers have passed away. I have heard these sons and daughters say they never fully thanked their mothers until it was too late to tell them.

    I am blessed with the dear mother who is still alive. I appreciate her devotion more each day. My mother does not change, but I do. As I grow older and wiser, I realize what an extraordinary person she is. It's sad that I am unable to say these words in her presence, but they flow easily from my pen.

    How does a daughter begin to thank her mother for life itself? For the love, patience and just plain hard work that go into raising a child? For running after a toddler（学步儿童）, for understanding a moody teenager, and for tolerating a college student who knows everything? For wailing for the day when the daughter realizes what her mother really is?

    How does a grown woman thank a mother for continuing to be a mother? For being ready with advice when asked or remaining silent when it is needed? For not saying “I told you so.” when she could have voiced these words dozens of times? For being essentially herself－loving, thoughtful, patient and forgiving?

    I don't know how to thank her, dear God, except to bless her and live up to the example she has set. I pray that I will look as good in the eyes of my children as my mother looks in mine.