A celestial body will cross the prime vertical circle when the latitude is numerically（）.

A chart projection depicting the poles and a small area on either side of a connecting meridian，that is sometimes used for star charts，is the（）.

A buoy with a composite group-flashing light indicates a(n)（）.

A chart with a natural scale of 1:160，000 is classified as a（）.

A “Mediterranean moor” should be used when（）.

A CO2 extinguisher on a ship which has lost 10% of its charge must be（）.

A chain bridle is used when towing astern because it（）.

A “reaching” course is one in which the wind（）.

A “sheepshank” is used to（）.

A tonnage tax is levied according to the（）.