25.下列何者為真性腫瘤（true neoplasm）？
(A)牙骨質母細胞瘤（cementoblastoma）
(B)齒瘤（odontoma）
(C)化膿性肉芽腫（pyogenic granuloma）
(D)血管瘤（hemangioma）

Cementoblastoma is an odontogenic neoplasm of cernentoblasts, and many authorities believe this neopiasm represents the only true neoplasm of cementum.  

Odontomas  are  considered  to  be  developmental  anomalies (hamartomas) rather than true neoplasms

the pyogenic granuloma is thought to represent an exuberant tissue response to local irritation or trauma . In spite of its name, it is not a true granuloma.

hemangiomas are considered to be benign tumors of infancy that are characte rized by a rapid growth phase with endothelial cell proliferation,followed by gradual involution.