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

In the Northern hemisphere northerly winds may cause temperature（）.

It is dangerous for vessels without the operational radar（）the estuary.

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

What is it called when it is possible to ignite the vapour above the oil?（）

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

The dew point temperature is（）.

Before any loading takes place any signs of the previous cargo should do（）.

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

The helm command PORT TWENTY means（）.