单项选择题
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
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?（）
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?（）
单项选择题 A diesel engine exposed to widely varying ambient temperatures should use to a lubricating oil with （）