- 搜標(biāo)題
- 搜題干
- 搜選項
單項選擇題
A heavy，thick-walled tube，usually steel，used between the drill pipe and the bit in the drill stem to weight the bit in order to improve its performance is called a（）.
A.heavy-walled drill pipe
B.tool joint
C.down hole tool
D.drill collar
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