单项选择题
A.70% B.80% C.90% D.93%
A.6×7 B.6×19 C.6×37 D.6×24
A.尼龙绳 B.乙纶绳 C.丙纶绳 D.维尼龙绳
A.①~⑥ B.①~⑤ C.①②③⑤ D.①②④⑤
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