97免费在线观看视频,亚洲综合自拍网,黄色毛片免费观看,热久久综合网,免费看日产一区二区三区 狠狠操av,久久久涩涩涩,在线精品免费视频,人人插天天干,久久91精品国产91久久

單項選擇題

Which one of three elements for a fire on a tanker vessel is most difficult to eliminate (isolate)?()

A.a combustible element, fuel
B.energy (resources for ignition) to start the combustion
C.oxygen to support the combustion
D.both A and C are correct

微信掃碼免費搜題