试举出四种常用刨床类机床的名称。
参考答案：
解析：刨床类机床有牛头刨床、龙门刨床、插床、单臂刨床等。
I regret ____ my teacher's advice, otherwise I would have succeeded in passing the exam. [ ]
A. not to take
B. not taking
C. not to have taken
D. having not taken
干扰电疗时，兴奋运动神经，使正常骨骼肌发生单收缩或使失神经肌发生收缩选用的差频是（）
A.100Hz
B.50～100Hz
C.25～50Hz
D.30～40Hz
E.1～10Hz
