单项选择题
A first magnitude star is（）.
A.2.5 times as bright as a second magnitude star B.3 times as bright as a second magnitude star C.5 times as bright as a second magnitude star D.10 times as bright as a second magnitude star
单项选择题 A double star is a star that（）.
单项选择题 A correction for augmentation is included in the Nautical Almanac corrections for（）.
单项选择题 A body can only be observed at lower transit when（）.
