The purpose of inert gas systems aboard tankers is to（）.

单项选择题The number or name of a tank barge shall be（）.

A.displayed in at least 4 different positions on the barge
B.carved on a wooden board and attached to the barge's hull
C.displayed as close to the navigation lights as possible
D.displayed at the highest point of the barge's hull such that it can be seen from either side

单项选择题The fresh air intake of the inert gas system（）.

A.prevents the flue gas from falling below 3% content of oxygen
B.allows the inert gas piping to be used for gas freeing the tanks
C.opens when there is excessive vacuum on the deck water seal
D.enables outside air to mix with and cool hot flue gasses

单项选择题The designations A，B，C，D and E grades of cargo refer to the（）.

A.degrees of quality of petroleum products
B.flash point range and Reid vapor pressure index of petroleum products
C.grades of crude oil
D.pour point，color，and viscosity index of petroleum products

单项选择题The deck water seal of the inert gas system（）.

A.cools the inert gas and prevents soot from entering the cargo tanks
B.acts as an emergency shutdown when inlet pressures exceed the safe working pressure
C.prevents the backflow of hydrocarbon gasses into nonhazardous areas
D.relieves sudden large overpressures in the system

单项选择题The component in an inert gas system used for cleaning the gas of solid and sulphur combustion products，while simultaneously cooling the inert gas，is called the（）.

A.filter
B.cooler
C.scrubber
D.purifier