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單項選擇題

Moisture should be kept out of an R-12 system because it tends to cause （）.

A.icing of the automatic controls
B.embrittlement of some parts of the automatic controls
C.sludge in the lubricating oil
D.all of the above

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單項選擇題

Black smoke coming from a boiler can be caused by （）.

A.low water level
B.high water level
C.excessively high fuel pressure
D.low oil temperature

單項選擇題

If a bilge pump failed to build up discharge pressure, you should check for （）.

A.excessive water in the bilges
B.a clogged suction strainer
C.oil in the bilges
D.All of the above

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