A circular table has a glass center with a diameter of 4x inches, which is surrounded by a metal ring with a width of 2 inches. In terms of x, what fraction of the table's surface is made up by the metal ring?
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A{1}\over{x+1}
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B{1}\over{x}
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C{x}^{2}\over({x+1})^{2}
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D{2x}+1\over({x+1})^{2}
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E{x}\over{x+1}
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正确答案: D