单项选择题
A.value of the mean draft
B.degree of list
C.amount of roll
D.difference in fore and aft drafts
单项选择题 The explosive range of a mixture of flammable vapors is specified as a percentage of （）.
单项选择题 What safety precautions should be observed by the crew while working around machinery in an engine room?（）
单项选择题 The word "discharge" as used in Pollution Prevention Regulations applies to oil （）.