单项选择题
The in the steering gear move the rudder to the required angel（）
A.control equipment
B.power unit
C.transmission mechanisms
D.fittings and pipeline
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相关考题
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单项选择题
Positive displacement, helical gear pumps are well suited for pumping oil because （）
A.stuffing boxes eliminate the leakage problems usually associated with other gear pumps
B.it is not necessary to closely maintain design clearances with this pump
C.they are essentially self-priming and produce a high suction lift
D.these pumps are designed with extreme tooth angled -
单项选择题
One of the reasons that causes oil flowed from sludge outlet of a self-cleaning purifier is （）
A.seal water supply be cut off
B.make-up water supply be cut off
C.oil outlet valve closed or not open sufficiently
D.the flow rate of oil is too much -
单项选择题
To ensure oil purifier working in normal condition,the interval between two sludge discharging should not exceed（） hours.
A.2
B.4
C.5
D.6
