Which of the following is not a form of precipitation?（）

Shipboard Emergency Drills must be carried out at least（）on board cargo ship.

A tide is called diurnal when（）.

The force resulting from the earth’s rotation that causes winds to deflect to the right in the Northern Hemisphere and to the left in the Southern Hemisphere is called（）.

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

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

According to the relevant regulation, lifeboat should be powered by（）.

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

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

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