安装时，罗茨流量计上游必须配置（），以改善介质的纯净度。
A.整流器
B.过滤器
C.稳压器
D.脉冲发生器
参考答案：B
The girl was most _______ when the young man offered to suck the poison out of the snake bite in her leg and ______ that he was a reliable man to marry.[ ]
A. moved; determined
B. affected; decided
C. touched; made up her mind
D. moved; was determined
下述哪种情况常提示亚急性感染性心内膜炎（）
A.期前收缩
B.心房颤动
C.心脏扩大
D.新出现病理杂音
E.原有的病理杂音强度增加Ⅱ级以上，或杂音的性质、强度突然改变
