气体灭火系统按其装配形式可分为（）。

A．全淹没系统

B．局部应用系统

C．管网灭火系统

D．无管网灭火系统

E．单元独立灭火系统

Antarctica is so mystically described by some people. If only I _____ there!  [ ]

A. had been    

B. have been        

C. have gone          

D. had gone