【EX-3-1-2】对一个初始为空的栈s执行操作Push(s,5),Push(s,2),Push(s,4),Pop(s,x),getTop(s,x)后，x的值应是（ ）。 A．5 B．2 C．4 D．0

A. 喉痉挛
B. 肺内误吸
C. 气胸
D. 舌后坠
E. 药物过敏

A、气罐储气Gas storage tank
B、地下储气underground gas storage
C、天然气的液化储存Liquefied storage of natural gas
D、液化石油气（LPG）调峰Liquefied petroleum gas (LPG) peak shaving
E、长输管道末段储气Gas storage at the end of long pipeline
F、天然气的溶解储存Dissolved storage of natural gas
G、天然气水合物（NGH）的固态储存Solid state storage of natural gas hydrate (NGH)
H、天然气吸附储存Natural gas adsorption storage