The cause of tooth decay is acid, which is produced by bacteria in the mouth. The acid removes minerals from tooth enamel, allowing tooth decay to begin; the saliva in your mouth encourages remineralization and neutralizes the acid. The rate at which bacteria in the mouth 5 produce acid depends on the amount of plaque [...]

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When Daniel Boone died peacefully in bed in his son Nathan’s elegant stone Missouri farmhouse on September 26, 1820, the surge of emigrants along the Oregon Trail was still a generation away. But Boone already exemplified the pioneer at his best. He was neither the physical 5 giant (five feet nine) nor the innocent child [...]

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This rapid transcontinental settlement and these new urban industrial circumstances of the last half of the 19th century were accompanied by the development of a national literature of great abundance and variety. New themes, new forms, new subjects, new regions, new authors, 5 new audiences all emerged in the literature of this half century. As [...]

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Until recently, most American entrepreneurs were men. Discrimination against women in business, the demands of caring for families, and lack of business training had kept the number of women entrepreneurs small. Now, however, businesses owned by women account for more than 5 $40 billion in annual revenues, and this figure is likely to continue rising [...]

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While most desert animals will drink water if confronted with it, for many of them the opportunity never comes. Yet all living things must have water, or they will expire. The herbivores find it in desert plants. The carnivores slake their thirst with the flesh and blood 5 of living prey. One of the most [...]

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