单项选择题
Extended cyclical variations in tensions will cause an anchor chain to break due to（）.
A.fatigue B.corrosion C.distortion D.abrasion
单项选择题 Cribbing is（）.
单项选择题 Compared to manila line，size for size，nylon line（）.
单项选择题 Chafing gear is used to（）.
