单项选择题
The vapor pressure of a gas is the pressure necessary to keep it in a(n)（）.
A.soluble state B.solid state C.liquefied state D.inert state
单项选择题 The tops of vents from gasoline tanks should terminate（）.
单项选择题 The storage device for nitrogen-pressurized hydraulic fluid，which is used in closing the blowout preventers is called the（）.
单项选择题 The shut off valve at the gasoline tank which can be operated from outside the tank space （）.
