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老年人易患骨质疏松症,是骨中缺少                                                         (   ) A.蛋白质            B.维生素C      C.铁           D.钙 答案:D It is really ___ useful dictionary and ___ dictionary every one of us needs.        A.an; a                 B.a; the               C.the; a                           D.a; a
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