The purpose of the deck seal in an inert gas system is to prevent（）.

A.allow sufficient oxygen in the tank to sustain life
B.prevent outside air from entering the tank
C.provide more discharge pressure
D.comply with pollution regulations

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

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