单项选择题
A.the Sun，Earth，and Moon are at right angles B.the Sun's declination is 0°and is moving south C.an inferior planet is at the maximum angle to the line of sight to the Sun D.the Earth is between a planet and the Sun
On mid-ocean waters，the height of a wind-generated wave...
单项选择题On mid-ocean waters，the height of a wind-generated wave is not affected by the（）.
A.water depth exceeding 100 feet B.fetch C.wind's velocity D.duration of the wind
Mars will not be visible（）.A.at elongation angles near ...
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
It is difficult to determine which limb of the Moon is ...
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
