单项选择题

A double star is a star that（）.

A.has a declination equal to twice that of the Sun
B.comprises two stars that appear close together
C.is twice as bright as a single star
D.suddenly becomes much brighter and then fades

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单项选择题

A correction for augmentation is included in the Nautical Almanac corrections for（）.

A.the Sun
B.the Moon
C.Venus
D.None of the above

单项选择题

A body can only be observed at lower transit when（）.

A.the declination is the opposite name to the latitude
B.the algebraic sum of the colatitude and declination exceeds 90
C.the observer is in high latitudes above either polar circle
D.the body is circumpolar