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單項選擇題

Those generally used additives for cooling water are either anti-corrosion oils or inorganic（）.

A.gases
B.paints
C.inhibitors
D.detergent

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單項選擇題

This used piston had been tested and approved as a spare part by the （） during last annual repair.

A.agent
B.shipchandler
C.surveyor
D.engineer

單項選擇題

They understand the （） of automatic sludge discharging of the purifierBut they are not good in practice.

A.principle
B.principal
C.cause
D.case

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