單項(xiàng)選擇題

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

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單項(xiàng)選擇題

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

單項(xiàng)選擇題

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