单项选择题
A.degrees of quality of petroleum products
B.flash point range and Reid vapor pressure index of petroleum products
C.grades of crude oil
D.pour point，color，and viscosity index of petroleum products
单项选择题 The deck water seal of the inert gas system（）.
单项选择题 The component in an inert gas system used for cleaning the gas of solid and sulphur combustion products，while simultaneously cooling the inert gas，is called the（）.
单项选择题 The combined fan discharge rate in an inert gas system is related to the（）.