我国目前习惯按()对阀门进行分类。
A.压力等级和结构形式
B.压力等级和用途
C.结构形式的用途
D.材质和压力等级
参考答案:A
呕血最常见的原因是()
A.胃底、食管静脉曲张破裂
B.食管癌
C.消化性溃疡
D.钩端螺旋体病
E.急性胃黏膜病变
All agreed to his suggestion that a bridge across the river__________.
A.built
B.be built
C.would build
D.should build