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?（）.

Manoeuvring information can not be obtained from（）.

When steering by autopilot,how often should the steering be checked?（）

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

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

Which wind results from a land mass cooling more quickly at night than an adjacent water area?（）

The dew point temperature is（）.

The circulation around a low pressure center in the Northern Hemisphere is（）.

Fog is likely to occur when there is little difference between the dew point and the（）.