When approaching a preferred-channel buoy，the best channel is NOT indicated by the（）.

A.the shape of an unlighted buoy
B.the light color of a lighted buoy
C.the color of the topmost band
D.whether the number is odd or even

A.Errors due to unusual parallax are eliminated
B.The same body can be used for a fix from observations separated by several minutes
C.The declination is the only information needed from the almanac
D.The semidiameter correction of the sextant altitude is eliminated