单项选择题
Emulsion oils and sodium nitrite are both approved additives, but the latter cannot be used if any pipes are （） or if any soldered joints exit.
A.chromed
B.welded
C.galvanized
D.bolted
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相关考题
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单项选择题
Either a low injection pressure or a leakage of piston rings is able to lead （）.
A.a high exhaust temperature
B.a high smoky exhaust
C.a high output
D.a high compression -
单项选择题
Each piston stuffing box is provided with two sealing rings and three（）
A.packings
B.piston rings
C.distributor rings
D.scraper rings -
单项选择题
Each journal and pin should be examined for （） and grooving.
A.bridges
B.recesses
C.rears
D.ridging
