A tug is to assist in docking an oceangoing vessel on a hawser. The greatest danger to the tug is （）.

During a period of whiteout，you should expect which of the following（）.

Due to lapse of time the risk in these areas to surface navigation is now considered （）than the ordinary risks of navigation，but a very real risk still exists with regard to anchoring，fishing or any form of submarine or seabed activity.

On a voyage from Capetown to London，the favorable ocean current off the coast of Africa is the （）.

Information on the operating times and characteristics of foreign radiobeacons can be found in which publication? （）

A vessel is entering port A for the first time and has a Pilot conning the vessel. The Master is unsure that the Pilot is taking sufficient action to prevent a collision. What should the Master do（）.

The height of tide is the （）.

At last，the palm trees that fringe the natural harbor of Port Aloahoa come into view on the horizon lit by the setting sun.The meaning of this sentence is that （）.

Attention is called to the fact that in many cases charted depths may be decreased by up to （）.

The height of a light is measured from which reference plane?（）