单项选择题
A.upon commencement B.on completion C.before ending D.after beginning
After riveting is completed，the joints on the shell of ...
单项选择题After riveting is completed，the joints on the shell of a vessel are generally made watertight by（）.
A.faying B.caulking C.felt or canvas packing D.red lead
A special device that，when fitted into the rotary table...
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
A self-contained breathing apparatus is used to（）.A.mak...
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
