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單項選擇題

Personnel working with refrigeration systems, and subject to the exposure of refrigerants should wear （）.

A.face shield
B.a respirator
C.rubber gloves
D.an all purpose gas mask

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單項選擇題

To absorb the wear resulting from impeller rotation and abrasives in the liquid, a centrifugal pump is usually fitted with （）.

A.lantern rings
B.bearings
C.easing volutes
D.wearing rings

單項選擇題

If the capacity of a centrifugal pump decreases gradually over a long period of time, you should replace the （）.

A.packing gland
B.mechanical seals
C.lantern rings
D.wearing rings