单项选择题
At sea，on what occasion would you display two red lights at night or two black balls during the day?（）.
A.When vessel is on fire B.When vessel is not under command C.When vessel is carrying the dangerous cargoes D.When vessel is restricted in her ability to maneuver
单项选择题 Argon is classified as a（）.
单项选择题 Another name for coal naphtha that would appear on a dangerous cargo manifest is（）.
单项选择题 All of our export dangerous goods are（）the standard.
