Out of the crowded bus _____, who was dressed in a black suit and waved to a woman. [ ]

A. a tall man in his thirties stepped

B. stepped a tall man in his thirties

C. did a tall man in his thirties step

D. did a tall man step in his thirties

肝硬化腹水产生的最主要原因是（）

A.血清白蛋白降低

B.门静脉压力增高

C.肾功能不全

D.脾功能亢进

E.便秘