（）is halfway between the forward and after perpendiculars and is reference point for vessel construction.

Despite the rising importance and great convenience of the gyrocompass,the magnetic compass still retain its importance because of its（）.

Full details of all lights and fog signals are shown on（）.

The mean draft of a ship is the draft（）.

When the wave period and the apparent rolling period are the same（）.

Manoeuvring information can not be obtained from（）.

ECDIS must be able to perform all of the following EXCEPT（）.

The helm command PORT TWENTY means（）.

Your vessel is docking, but not yet alongside. Which line will be the most useful when maneuvering the vessel alongside the pier?（）.

The company should establish and maintain procedures to control all documents and date which are relevant to（）.