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

单项选择题When a buoy marks a channel bifurcation，the preferred channel is NOT indicated by（）.

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

单项选择题What is the major advantage of high altitude observations?（）

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

单项选择题What is the light characteristic of a lighted，preferred-channel buoy? （）

A.Group flashing
B.Composite group flashing
C.Interrupted quick flashing
D.Fixed and flashing

单项选择题What indicates a dual purpose buoy? （）

A.Red buoy with a horizontal yellow band
B.Red and white vertically-striped buoy with a vertical yellow stripe
C.Red and white vertically-striped buoy with a red spherical topmark
D.Green buoy with a yellow square

单项选择题What describes an accurate position that is NOT based on any prior position? （）

A.Dead-reckoning position
B.Estimated position
C.Fix
D.Running fix