焊缝中形成气孔的气体主要是氢气和一氧化碳，此外还有（）。
参考答案：氮气
简述电视媒体的优、缺点。
To remedy a leaking fire hose connection at the hydrant，secure the valve and（）.
A.replace the gasket in the male coupling
B.reduce fire pump pressure
C.replace the gasket in the female coupling
D.rethread the male coupling
