单项选择题

Mars will not be visible（）.

A.at elongation angles near 180°
B.from quadrature to opposition
C.at conjunction
D.at opposition

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单项选择题

It is difficult to determine which limb of the Moon is fully illuminated（）.

A.when the Moon is low in the sky at rising or setting
B.at the new Moon phase
C.when taking Moon sights during daylight
D.when the terminator is nearly vertical

单项选择题

In working out a local apparent noon sight for your latitude，you subtract the Ho from 90°. The 90°represents the angular distance from（）.

A.the equator to the elevated pole
B.your horizon to your zenith
C.your zenith to the elevated pole
D.the geographical position of the Sun to the elevated pole

单项选择题

In the navigational triangle，the angle at the elevated pole is the（）.

A.meridian angle
B.altitude
C.right ascension
D.azimuth angle