单项选择题
A.4~6倍 B.7~8倍 C.2~3倍 D.7.5~8.5倍
A.5mm B.10mm C.15mm D.20mm
A.0.2m B.0.5m C.0.8m D.1m
A.接头部分的外径 B.钻杆本体外径 C.钻杆本体内径 D.接头处内径
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