單項(xiàng)選擇題

A star is observed at lower transit. The line of position derived from this sight is（）.

A.on the prime vertical
B.a latitude line
C.a longitude line
D.of no special significance

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A sidereal day is shorter than a solar day. This difference is due to（）.

A.irregularities in the daily rotational rate of the Sun
B.the space motion of the solar system
C.the precession of the equinoxes
D.the use of different reference points

單項(xiàng)選擇題

A sidereal day is approximately how much shorter than a solar day?（）

A.4 minutes
B.8 minutes
C.12 minutes
D.16 minutes