单选题The amount of fluid delivered by a helical pump can be regulated by （）.Athrottling the pressure lineBchanging the speed of the rotorCeither A or BDNone of the above is tree
单选题
The amount of fluid delivered by a helical pump can be regulated by （）.
A
throttling the pressure line
B
changing the speed of the rotor
C
either A or B
D
None of the above is tree
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