大国在处理国际事务中的作用举足轻重，深刻影响着世界历史发展的进程。阅读下列材料，回答问题：

材料一  捷克斯洛伐克外交部长说：“我不知道你们的国家是否会从慕尼黑做出的决定中得到好处，但肯定无疑的是，我们不会是最后一个受害者。在我们之后，其他人也将遭遇同样的命运。”

——北师大版《历史》九年级下册

材料二   1945年2月3日，美、英、苏三巨头聚在一个名叫雅尔塔的小镇进行秘密谈判。会谈的目的是美、英双方希望苏联尽早落实对日宣战的时间，苏联则为此提出诸多要求，有许多内容涉及到中国的主权。罗斯福为了尽快让苏联出兵以减轻美军的伤亡，对于斯大林的要求并未加以拒绝，只是认为涉及外蒙古、大连商港和旅顺军港以及中长铁路的相关协议需要征求蒋介石的同意，而斯大林则建议此事应由罗斯福向蒋介石通告，并保证获得其同意。然而三方在会谈后发表的公告中，却对这些内容只字未提。

6月10日，美国大使奉总统的命令，向蒋介石当面报告有关雅尔塔会议中苏方提出的参战条件……这下子蒋介石真的被激怒了，斯大林对中国充满野心他是预料到的，但他没有想到的是，美国总统居然为了本国的利益，真的会牺牲他国的权益。至于谈判的最终结果，斯大林得到了他想要的一切。

——郑会欣《“忍气吞声，负重致远”：从蒋介石日记看他对雅尔塔协议的态度》

材料三   1945年后，经济冲突与共产王义和资本王义在意识形态的抵触是一致的……然而意识形态上的相互猜忌，却使美苏之间的利益冲突转为情感上的不合。双方都逐渐相信，对方企图摧毁自己的一切生活方式。包围与颠覆——这对孪生妖孽，在双方似乎能证实自己的假设不虚时，使真正成为一种存在的实体了。

——（美）罗伯特·帕克斯顿《西洋现代史》

已知随机变量ξ满足Dξ=2，则D（2ξ+3）=____．

在一定地域内，____与____ 所形成的统一整体叫做生态系统．生态系统的生物部分包括____、消费者、分解者；非生物部分有____ 、温度、水等．

①甲、乙两个水杯中，盛有热水的是____；

②该实验说明分子热运动的剧烈程度与____有关．

    Do you know any 9-year-olds who have started their own museums? When Theodore Roosevelt was only nine, he and two of his cousins opened the "Roosevelt Museum of Natural History". The museum was in Theodore's bedroom. It had a total of 12 specimens. On display were a few seashells, some dead insects, and some birds' nests. Young Roosevelt took great pride in his small museum.

    Born in New York in 1858, Theodore Roosevelt was not always healthy. "I was a sickly boy", he once wrote. Roosevelt had a health condition called asthma. He often found it hard to breathe. Instead of playing, he watched nature and then read and wrote about it.

    Roosevelt's interest in nature sometimes got him into trouble. Once, his mother found several dead mice in the icebox. She demanded that the mice be thrown out. This was indeed "a loss to science", Roosevelt said later.

    Because Roosevelt was often sickly as a boy, his body was small and weak. When he was about 12, his father asked him to improve his body. Roosevelt began working out in a gym. He didn't become strong quickly. But he did decide to face life's challenges with a strong will. That determination stayed with Roosevelt his whole life. And eventually his body did get strong. As an adult, he was an active and healthy person. He enjoyed adventures, and he loved the outdoors.

    A toy company named the teddy bear for Theodore "Teddy". After knowing that, Roosevelt refused to shoot a baby bear while hunting.

    In 1900, at the age of 41, Roosevelt was elected Vice President. A year later, President McKinley, was shot and killed. Roosevelt became our 26^th President. At 42, he was the youngest leader the country had ever had.