单项选择题
Safe welding practice requires （）
A.checking the area for items that may catch fire
B.that a fire watch be posted
C.checking for the explosive gases
D.all of the above
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相关考题
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单项选择题
Which lubricating oil additive is used in diesel engines to reduce the tendency for sludge and varnish to form on the engine parts?（）
A.Flash point improvers
B.Pour point improvers
C.Inhibitors
D.Foam suppressors -
单项选择题
Which of the following characteristic of lube oil helps to reduce the amount of deposits in the piston ring belt during the combustion process in a diesel engine?（）
A.Low viscosity index
B.Low carbon forming tendencies
C.High film strength
D.High non-corrosive qualities -
单项选择题
A diesel engine exposed to widely varying ambient temperatures should use to a lubricating oil with （）
A.a high viscosity index
B.a low viscosity index
C.neutralize acids
D.resist oxidation at high temperatures
