单项选择题
Cargoes which（）an explosive，inflammable，poisonous and corrosive nature are called dangerous goods.
A.is B.are of C.is of D.are
单项选择题 Can we change the location for the tung-oil（）that for the gum rosin?
单项选择题 Calcium carbide and acetone are counteractive（）nature.
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?（）.
