活塞销的主要损坏形式是_______ I. 磨损,II. 摩擦,III. 擦伤,IV. 腐蚀,V. 裂纹
A. I+II+V
B. I+V
C. II+V
D. I+III+V
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一个经济衰退的标准定义是实际GDP的下降持续至少两________。
A. 年
B. 季度
C. 月份
D. 星期
E. 参考期间
what chemicals did you use to treat the boiler water ?when you test alkalinity and acidity of water in boiler by pH test paper ? the result shows the boiler water is in acidiity . please describe what the possible cause is .
Which of the following components are used to convert alternating current produced in the
Armature and equalizer
B. Commutator and brushes
C. Rotor and interpoles
D. Field and exciter