单项选择题
A.60° B.90° C.135° D.150°
A.R=（0.53〜0.6）D B.R=（0.35〜0.4）D C.R=（0.45〜0.48）D D.R=（0.65〜0.8）D
A.D≥（e-1）D B.D≥（e-2）D C.D≥（e-3）D D.（D≥（e-4）D（式中e为钢丝绳的系数）
A.5% B.10% C.15% D.20%
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