Some blood types are quite common，others are regionally______，and still others are rare everywhere.

A．distributed

B．contributed

C．obtained

D．convinced

患者近半年体重下降明显，肝脏超声可见肝右叶结构紊乱，回声不均，门静脉右支充满稍高实性回声，门静脉可能形成了（）。

A.血栓

B.静脉瘤

C.血管瘤

D.癌栓

E.静脉扩张