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科学家在合成超导材料时,偶然制得了在自然界尚未发现的紫色化合物BaCuSi2O6,它由____种元素组成.

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    When I entered college, I took Professor Black's poetry class. Even though I finished every task and1no classes, I earned a “C” at the end of the term. Frustrated, I went to his office and asked in a low voice, my knees2, “Do I have any talent?” He was a kind person. He pushed his hair behind his ears3he was thinking. “Probably not,” he said4. “Thank you,” I said, feeling like a grafted (嫁接的) apple tree: part of me discouraged, another part5to accept it.

    The latter part led me to another poetry class by Professor White. This time, I earned an “A”. Professor White told me that6in his class earned an “A”. I was shocked. His7approach reminded me of Professor Black, from whom I learned teachers don't hold the keys to their students'8.

    Every human being is9born with talent. Some10souls are born with many talents. People are11to subjects they have a gift for,12nearly everyone in the writing class has writing talent.

    But no one can13whether or when talent will bloom (绽放) into art that others14as good. Some people bloom early, others late, some not at all. Artists must have enough15to make art, and trust their own pleasure in making it. It was really the faith in myself as well as the16in writing poems that helped me17many years of writing poems without being recognized.

    I've been teaching creative writing for more than 30 years. Students sometimes ask me, “Do I have talent?” I tell them my18, and say, “Of course you do. But just19writing no matter whether anyone approves (认可,赞成)-or even 20.”

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    彗星主要是由冰构成的──水(H2O)冰,还有少量的甲烷(CH4)冰和一些氨(NH3)冰。在撞击地球的大气层时,一个中等大小的彗星碎片会产生一个白炽的火球和一种巨大的冲击波。火球会烧毁树木,冲击波会扫平森林,它的声音还会波及全球。但是这样的彗星不太可能在地上撞出一个环形山。彗星上的冰块在进人大气层的时候全部融化了,因此不会幽灵般地出现,这种现象令人不安地向人们关于宇宙是万古不变、井然有序这一观念进行挑战。如果那条天天随着星星起落的壮丽的乳白色光带是无缘无故地出现在那里,与人间世事毫无关系,那简直是不可思议的。因此出现了这样的观点:彗星是灾难的预兆,是神谴的预兆──它们预示了帝王的终日,王国的崩溃。对于彗星,巴比伦人认为是天髯,希腊人认为是垂发,阿拉伯人认为是燃烧的剑。在托勒密时代,人们根据彗星的形状把它们分类为“梁”、“喇叭”。“坛子”等。托勒密认为彗星给人类带来战争、炎热的气候和“动乱”。中世纪的一些彗星图看上去像未探明的飞行的十字架。一个名叫安德烈亚斯·西利奇厄斯的马格迪堡路德教主管人(即主教),在1578年发表了一篇题为“新彗星的科学启示”的文章。他在文章中。提出了一个独特的观点,他说彗星是“人类罪恶的浓烟,每天、每时、每刻都在升腾,它在上帝面前丑态百出、胆战心惊,逐渐地由浓烟形成长着卷发梳着辫子的彗星,最后被天国最高法官的怒火烧着了”。但是另一些人反驳说,如果彗星是罪恶的浓烟的话,天空势必乌烟滚滚。


                                                                                                          ──选自《宇宙的边疆》(第四章)