用基圆滚动刨削叶轮渐开线齿面时，用校刀样板对刀，使两刀尖间距离（）叶轮的宽度。
A.等于
B.略大于
C.略小于
参考答案：A
According to a survey, homework is_____ students most often blame for their lack of sleep.[ ]
A. what
B. that
C. which
D. why
男性，70岁。排尿困难2年。腹部平片提示膀胱区有2．0cm椭圆形致密影。患者典型的临床症状是（）
A.膀胱刺激症状
B.进行性排尿困难
C.血尿
D.腰痛、血尿、脓尿
E.尿流中断，改变体位后好转
