单项选择题
A.How they finished
B.How did they finished
C.That how they finished
D.That how did they finished
单项选择题 Which of the following represents the maximum percent of oxygen by volume required to be achieved by a ship’s inert gas system, prior to the commencement of crude oil tank washing?（）
单项选择题 The fire of burning paper is classified as（）fire.
单项选择题 The fire of electrical equipment is classified as（）fire.