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【单选题】
酒精发酵的过程中释放出什么气体?A.
二氧化氮
B.
过氧化氢
C.
硫化氢
D.
二氧化碳
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【简答题】企业可以在不同的会计期间随意采用不同的会计处理方法。 （ ）
【判断题】Dynamic pumps are classified as centrifugal or axial. axial pumps operate on the principle of centrifugal force.
A.
正确
B.
错误
【单选题】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
【单选题】Centrifugal pumps have what advantage（s）over reciprocating pumps ________．
A.
They are less expensive
B.
They are smaller for equivalent pumping ability
C.
They pump more cargo in less time
D.
All of the above
【单选题】our long business relations and our amicable cooperation prospects, we suggest that you accept our terms.
A.
In that
B.
In view of
C.
For which
D.
Because of
【单选题】Most pump manufacturers recommend that the suction piping dimension for centrifugal pumps be _____.
A.
one size smaller than the pump suction nozzle
B.
the same size as the pump suction nozzle
C.
one size larger than the pump suction nozzle
D.
installed with a short radius elbow at the pump
【单选题】Which of the listed statements is correct concerning the starting of centrifugal pumps? .
A.
They should always be started with the discharge valve closed
B.
They should always be started with the discharge valve opened
C.
A priming pump is always required to flood the impeller suction
D.
They should always be started with the sealing line valves closed
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