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單項選擇題

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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單項選擇題

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

單項選擇題

Each piston stuffing box is provided with two sealing rings and three（）

A.packings
B.piston rings
C.distributor rings
D.scraper rings

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