单项选择题
It is more economical to use （）, because of their greater strength and longer useful lives.正确答案A
A. nylon ropes B. manila ropes C. sisal ropes D. wooden ropes
单项选择题 Natural fiber rope is made （）the fibers of different plants.
单项选择题 Wire rope needs （）care than hemp and manila.
单项选择题 （）is the strongest and the most elastic of all the synthetic fiber ropes.
