单级离心泵是指轴上有（）个叶轮。
A.1个
B.2个
C.3个
D.4个
参考答案：A
She was complaining that the doctor was________too much for the treatment he was giving her.[ ]
A. spending
B. offering
C. costing
D. charging
属于一级预防的是（）。
A.早发现
B.社会康复
C.健康教育
D.康复治疗
E.子宫颈癌筛检
