C Recently the World Health Organization announced that the disease of smallpox（天花）had almost been wiped out in most parts of the world, thanks to widespread vaccination（种牛痘）. Most
The Atlantic Ocean is one of the oceans that separate the Old World from the New. For centuries it kept the America from being discovered by the people of Europe. Many wrong ideas about the Atlantic m
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量的高锰酸钾固体制氧气，下图所示的四个图象，能正确表示对应变化关系的是