单项选择题
Which of the following gases represents the greatest threat to personnel safety in an engine room where the exhaust is leaking from a diesel engine?（）
A.Carbon dioxide B.Carbon monoxide C.Carbon trioxide D.Hydrogen sulfide
单项选择题 Seawater may be used for drinking water （）.
单项选择题 A class "D" fire would be considered as burning （）.
单项选择题 One of the methods NOT usually allowed in cleaning up oil spills in the United States is （）.
