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

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

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

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

A tide is called diurnal when（）.

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

The dew point temperature is（）.

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

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

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