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

The distance between the surface of the water and the tidal datum is the （）.

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（）.

Above-normal tides near the center of a hurricane maybe caused by the （）.

A pilot vessel on pilotage duty at night will show sidelights and a sternlight （）.

On a voyage from Halifax,N.S.,to Dakar,West Africa,the Canary Current will （）.

The height of tide is the （）.

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.

A vessel not to impede the passage of another vessel is not relieved （） taking collision-avoiding action.

Conditions for crossing a rough bar are usually best at （）.