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

Fusible-link fire dampers are operated by().

A.a break-glass and pull-cable system
B.electrical controls on the bridge
C.a mechanical arm outside the vent duct
D.the heat of a fire melting the link

微信掃碼免費搜題