Hello, Tim! What's that?

It's      eraser. And It's _______white eraser.[ ]

A. a, a        

B. an, a        

C. the, an        

D. 不填, a

门静脉高压症时受影响最早的侧支血管为（）

A.脐静脉

B.胃冠状静脉

C.直肠上静脉

D.腹膜后静脉

E.腹壁上静脉