33.下列何者為骨頭之惡性腫瘤? (A)骨之纖維發育不全(fibrous dysplasia) (B)骨纖維瘤(ossifying fibroma) (C)中央巨細胞瘤(central giant cell granuloma) (D)Ewing's肉瘤(Ewing's sarcoma)