单选题Most drill ships and barges have a walled opening below the derrick，open to the water’s surface and through which various drilling tools can pass down to the sea floor called a （）.A moon poolB spider deck openingC pontoonD keyway

A frame with two，or sometimes four，arms through which are threaded the guidelines and which is used to keep the drill stem and bit in line with the center opening in the temporary guide base is the ______.

A.drill stem guide

B.guide frame

C.drill string frame

D.casing guide

I have ______ damage below water line.

A.large

B.big

C.important

D.major

A、most of them

B、most of which

C、most of that

D、most of what

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

Which statement about ships operating in ice is FALSE ________．

A.Light and partly loaded ships should be ballasted as deeply as possible

B.In brash-filled channels，operating with a shallow draft forward is most effective

C.Traditionally，operating ships light in the ice has been effective in the spring

D.Good searchlights should be available in the event of night navigation with or without icebreaker escort

The Port Authorities, in accordance with the IMO resolutions have been carrying out _____ to enhance safety of ships.

A.CPP

B.FPP

C.FSC

D.PSC