单项选择题
A.An oxygen indicator B.A combustible gas indicator C.A combination combustible gas and oxygen indicator D.A flame safety lamp
What is the BEST conductor of electricity?（）A.Carbon di...
单项选择题What is the BEST conductor of electricity?（）
A.Carbon dioxide B.Distilled water C.Fresh water D.Salt water
Upon completion of fueling a gasoline driven vessel it ...
单项选择题Upon completion of fueling a gasoline driven vessel it is necessary to（）.
A.keep ports，doors，windows，and hatches closed B.start engines immediately C.ventilate before starting engine D.None of the above
There are（）rats on board.A.notB.noC.anyD.none
单项选择题There are（）rats on board.
A.not B.no C.any D.none
