单项选择题
Calcium carbide and acetone are counteractive（）nature.
A.by B.in C.from D.with
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?（）.
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（）.
