单项选择题
A.2.0~2.5 B.2.5~3.0 C.3.0~3.5 D.3.5~4.0
A.临时仰拱B.地表锚杆C.管棚D.钢拱架
A.20mm B.30mm C.40mm D.50mm
A.100~200mm B.150~250mm C.200~300mm D.150~300mm
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