蜗轮、蜗杆工作时齿面磨损与圆柱齿轮传动相比（）。
A、轻微
B、严重
C、一样
D、无法确定
参考答案：B
You can trust him because he always ________.
A．keeps his words
B．stick to his promise
C．keeps his word
D．keep his promise
顽固性高血压，上腹部可闻及血管性杂音（）
A.肾动脉狭窄
B.原发性醛固酮增多症
C.尿毒症
D.皮质醇增多症
E.嗜铬细胞瘤
