所有植物的种子均具有()。 ["相同的子叶数","胚乳","胚","胚轴"]
斜面升船机斜架车(承船厢)底部设置有平衡油缸,如果发现平衡油缸不平衡时,应进行相应的()。 ["A、调整","B、加油","C、补充","D、减油"]
在精研磨内孔时,先进行粗研磨,然后再进行半精研磨,最后用()的研磨粉进行精研磨。 ["A、M9~M11","B、M5~M7","C、M7~M9","D、M1~M3"]
应经常清理供电轨道上面的灰尘、杂物,并涂以润滑油脂,该油脂必须满足()良好。 ["A、润滑","B、性能","C、导电","D、质量"]
万能外圆磨床为防止工作台有微动,需精密研磨节流阀与阀体孔,其圆度要求()。 ["A、0.001~0.002mm","B、0.015~0.03mm","C、0.03~0.05mm","D、0.1~0.25mm"]
渣油主要由哪些元素组成?其烃类按结构不同分几种?