单项选择题
A.1 B.5 C.8 D.10
A.2 B.3 C.4 D.5
A.R≥3D(钢管外径),L≥1.1D(但不大于60m B.R≥3D(钢管外径),L≥1.3D(但不大于60m C.R≥5D(钢管外径),L≥1.1D(但不大于60m D.R≥5D(钢管外径),L≥1.3D(但不大于60m