单项选择题
Before a tank is to be crude oil washed，the oxygen content in the tank must be measured at a position（）.
A.immediately above the level of the oil
B.at the top of the tank
C.in the vent riser
D.one meter from the deck
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相关考题
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单项选择题
Backfire flame arrestors are installed on（）.
A.fuel tanks
B.spark plugs
C.carburetors
D.distributors -
单项选择题
Automatic fire dampers in ventilation systems are operated by use of（）.
A.remotely operated valves
B.fusible links
C.C02 system pressure switches
D.heat or smoke detectors -
单项选择题
Automatic fire dampers in ventilation systems are operated by a（）.
A.remote operated valve
B.fusible link
C.CO2 system pressure switch
D.heat or smoke detector
