在风湿性心脏病中，下列瓣膜病变最常见的是（）

A.单纯二尖瓣狭窄

B.二尖瓣关闭不全

C.二尖瓣狭窄合并关闭不全

D.主动脉瓣狭窄

E.主动脉瓣关闭不全

Theodore Dreiser belonged to the school of literary ______ which .emphasized heredity and environment as important deterministic forces shaping individualized characters who were presented in special and detailed circumstances.

A. naturalism



B. realism
C. determinism



D. humanism