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(xiàng)選擇題

A common class of wire rope used for mooring is the 6x19 class. What does the 6 represent?()

A.Factor of safety
B.Number of wires per strand
C.Number of strands per wire rope
D.Number of wires in the core

微信掃碼免費(fèi)搜題