99色精品-9色在线-99色在线-99色视频 国产欧美日产一区二区三区_亚洲精品亚洲人成在线观看_四虎在线精品永久观看_免费一级a一片久久精

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