单项选择题
A special device that，when fitted into the rotary table，transmits torque to the kelly and simultaneously permits vertical movement of the kelly to make the hole is called a（）.
A.master bushing
B.kelly slips
C.kelly bushing
D.rotary bushing
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A self-contained breathing apparatus is used to（）.
A.make underwater repairs to barges
B.determine if the air in a tank is safe for men
C.enter areas that may contain dangerous fumes or lack oxygen
D.resuscitate an unconscious person -
单项选择题
A damaged T-Boat that is unable to meet the requirementsof its Certificate of Inspection but is able to travel to a shipyard under its own power should（）.
A.make the trip only after obtaining a Permit to Proceed to Another Port for Repair，Form CG-948
B.get underway as soon as possible
C.hire a tug and pilot instead
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单项选择题
A bridge over a navigable waterway is being repaired. There is a traveller platform under the bridge’s deck that significantly reduces the vertical clearance. If required by the CG district commander，how will this be indicated at night?（）
A.Illumination by flood lights
B.A quick flashing red light at each lower corner
C.A strobe light visible both up and downstream
D.Fixed amber lights under the extreme outer edges of the traveller
