单项选择题
The purpose of inert gas systems aboard tankers is to（）.
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
单项选择题 The number or name of a tank barge shall be（）.
单项选择题 The fresh air intake of the inert gas system（）.
单项选择题 The designations A，B，C，D and E grades of cargo refer to the（）.
