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 large valve，usually installed above the ram preventers，that forms a seal in the annular space between the pipe and wellbore or，if no pipe is present，on the wellbore itself is called the（）.

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（）.

An inert gas system on a tanker should be used to（）.

A fire is discovered in the bow of your vessel while making way. The wind is from ahead at 35 knots. You should（）.

A large vessel is equipped with a controllable pitch propeller. Which statement is TRUE?（）

How could lashing gear used aboard Ro-Ro vessels be stowed when not in use? （）

A hand held instrument used to measure distances between objects and the ship is a（）.

Between 1830 hrs and 1850 hrs this day，strong gusty winds（）by my vessel，in consequence of which the vessel’s four mooring lines were broken.

Cargo transfer operations on a tank vessel need NOT be stopped when（）.