单项选择题
The storage device for nitrogen-pressurized hydraulic fluid，which is used in closing the blowout preventers is called the（）.
A.actuator B.annulus C.accumulator D.annular preventer
单项选择题 The shut off valve at the gasoline tank which can be operated from outside the tank space （）.
单项选择题 The primary hazard of liquefied petroleum gas and liquefied natural gas is（）.
单项选择题 The amount of LFG that may be loaded into a given tank is determined by（）.
