單項(xiàng)選擇題An amplitude of the Sun in high latitudes（）.

A.is most accurate before sunrise
B.is most accurate after sunset
C.should only be observed when the Sun's lower limb is above the horizon
D.is most accurate when the Sun's center is observed on the visible horizon


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1.單項(xiàng)選擇題Altair is found in what constellation?（）

A.Hercules
B.Cygnus
C.Aquila
D.Capricorn

2.單項(xiàng)選擇題After Venus passes the point of greatest elongation east in its orbit，the first position in which the elongation will be zero is（）.

A.superior conjunction
B.inferior conjunction
C.opposition
D.None of the above; the elongation will never be zero

3.單項(xiàng)選擇題A variable star is one that（）.

A.exhibits a change in magnitude
B.has a changing declination
C.is increasing in SHA
D.is also known as a red giant

4.單項(xiàng)選擇題A star that suddenly becomes several magnitudes brighter and then gradually fades is a（）.

A.double star
B.variable star
C.nova
D.nebula

5.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