單項選擇題The approximate positions of the stars are based on sidereal time，which is based upon rotation of the Earth relative to（）.

A.winter solstice
B.autumnal equinox
C.summer solstice
D.vernal equinox


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2.單項選擇題The angle at the pole measured through 180°from the prime meridian to the meridian of a point is known as（）.

A.the departure
B.the polar arc
C.longitude
D.Greenwich hour angle

3.單項選擇題The altitude at LAN may be observed by starting several minutes in advance and continuing until a maximum altitude occurs. This procedure should not be used（）.

A.when the declination and latitude are of different names
B.when the declination is greater than and the same name as the latitude
C.if the vessel is stopped or making bare steerageway
D.on a fast vessel on northerly or southerly headings

4.單項選擇題Superior conjunction occurs when（）.

A.the Sun is at maximum declination north or south
B.a planet crosses the external plane of the ecliptic
C.the Sun is between the Earth and a planet
D.two planets are in line

5.單項選擇題Sidereal time is used by navigators when（）.

A.used with the equation of time
B.used in the form of LHA Aries
C.calculating the time of moonrise
D.determining local apparent time