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股票在中国的历史，可以追溯到19世纪洋务运动时期。当时中国出现了一批官办与官商合办的股份制企业。1873年成立的轮船招商局，发行了中国最早的股票。1914年，中国北洋政府颁布证券交易所法，1917年成立了北京证券交易所。到抗日战争前，上市股票已达百余种。但后来几经挫折，股市始终没有发展起来。对这段文字概括最恰当的是（）。
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Oceanography has always been regarded as the science of our oceans mixing geology, biology, chemistry, and physics to unveil the secrets of our seas. Scientists once defined oceanography as "the application of all sciences to the study of the sea". Before the nineteenth century, very few scientists showed an interest in the sea. Newton, a well-known scientist, explored some aspects of it theoretically in his works at one time, but later he was unwilling to have a further study on it.The sea was remote for the majority of the people, and except early travelers who traveled among continents or others who earned a living by undersea living creatures, it was not necessary to raise questions about it, let alone to ask what lay beneath the surface. Just when Europe and America proposed to lay a telegraph cable between them, the question "what is at the bottom of the seas" had to be answered for the first time with some commercial links. The engineers had to observe and measure the depth profile of the route to estimate the length of the cable to be produced.Thanks to Maury, the US Navy, the Atlantic Telegraph Company acquired information on this matter in 1853. In the 1840s, Maury had been assigned to encourage voyages during which soundings (测声) could be used to investigate the depths of the North Atlantic and Pacific Oceans as well. Later, some of his findings drew much attention and gained popularity in his book The Physical Geography of the Sea. The cable was laid, but the connection was not made permanent and reliable until 1866. At the early attempts, the cable failed and when it was taken out for repairs, it was found to be covered with living growths. The fact once refuted scientific argument at that time that there was no life in the deeper parts of the sea.Oceanography was gradually developed in next few years. In 1872 Thomson led a scientific expedition(考查) lasting for four years and brought back thousands of samples from the sea. Scientists were devoted to the classification and analysis of these samples for years and produced a five-volume report with the last volume published in 1895. Who asked Maury for help in oceanographic studies（）
多黏菌素类抗生素的作用机制是
已知m、n是方程x2-3x+1=0的两个实根，则2m2+4n2-6n的值为（）。
近代以来，中国社会内忧外患，正是这种严酷现实的强烈刺激，使知识分子的社会责任感变得特别______，而只要有这份责任感在心中______，那先前已经被理智放逐的传统意识，那注重世俗功利和群体价值的精神习惯，就很容易______。依次填入划横线部分最恰当的一项是（）。
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