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（）.

单项选择题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
D.request an Expiration Certificate if the vessel displays a tendency to sink

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

单项选择题（）of the following items is not in the charge of Chief Officer in repairing operation.

A.hull cleaning
B.derusting and painting
C.the maintenance of boiler
D.docking and undocking

单项选择题（）about 20 sq.m to be sand-blasted.

A.The rusting area
B.The rusted area
C.The corroded area
D.The corrosive area