You are inspecting the lower main precision bearings on a diesel engine.You observe that about half the thin Babbitt linings are of a milky white colourThis condition is caused by ()
A. large dirt particles in the oil supply
B. insufficient lubricating oil and overheating
C. normal wear
D. water contamination of the lube oil
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腰转动式可以补养和加强双臂、腰部、背部和髋关节。腰部器官得到按摩。
A. 正确
B. 错误
画规的两脚开合松紧要(),以免划线时发生自动张缩,影响划线质量。
A. 紧
B. 松
C. 适当
D. 较紧
同一水平行驶机车台数()及以上时,使用“信、集、闭”系统并使用正常。
A. 4台
B. 5台
C. 6台
D. 7台
制约儿童心理发展的因素有__________、__________、__________、__________及主观能动因素。