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單項選擇題

The internal part of boiler should be welded by yard if found （）.

A.sealed
B.cracked
C.shape changed
D.deformed

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單項選擇題

The internal part of the boiler, if found （）, has to be chemically washed by yard.

A.deformed
B.rusted
C.cracked
D.scaled

單項選擇題

Centrifugal pumps can be designed with a number of impellers （） to attain a high final delivery pressure.

A.in series
B.in parallel
C.either A or B
D.None of the above is tree