单项选择题
A.sunrise B.1200 LMT C.sunset D.2400 LMT
In general，the most effective period for observing star...
单项选择题In general，the most effective period for observing stars and planets occurs during the darker limit of（）.
A.sunset B.civil twilight C.nautical twilight D.astronomical twilight
Elongation becomes zero at（）.A.oppositionB.west quadrat...
单项选择题Elongation becomes zero at（）.
A.opposition B.west quadrature C.apogee D.inferior conjunction
During one synodic rotation，a body makes one complete t...
单项选择题During one synodic rotation，a body makes one complete turn relative to the（）.
A.Earth B.Sun C.stars D.vernal equinox
