单项选择题
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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相关考题
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单项选择题
A heavy steel curved arch constructed athwartships and above the after deck on a towing vessel is sometimes called a（）.
A.main brace
B.tow span
C.jockey bar
D.None of the above -
单项选择题
A head-on situation at night is one in which you see dead ahead a vessel showing（）.
A.one sidelight
B.one sidelight and a masthead light
C.one sidelight and two masthead lights
D.both sidelights of a vessel and her masthead light(s) -
单项选择题
A hand held instrument used to measure distances between objects and the ship is a（）.
A.vernier
B.psychrometer
C.hygrometer
D.stadimeter
