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單項選擇題

High-speed rotating in a centrifugal purifier can produce a force （） larger than the force of gravity.

A.many thousand times
B.between times
C.one time
D.at times

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單項選擇題

Here some oil in the oily water separator, as a result of its lower （）, will separate and rise into the oil collection space.

A.temperature
B.viscosity
C.density
D.velocity

單項選擇題

Heat energy is a source of power, but （） will cause damage to the engine.

A.excessive heat
B.insufficient heat
C.effective cooling
D.high output