An unhappy childhood may have some negative effects on a person's characters however, they

are not always_________.[ ]

A. practical      

B. avoidable        

C. permanent        

D. beneficial

肾前型急性肾衰竭常见的原因（）

A.肾中毒

B.挤压伤

C.大出血、休克

D.双侧输尿管结石

E.蛇咬伤