單項(xiàng)選擇題

The equator is（）.

A.the primary great circle of the Earth perpendicular to the axis
B.the line to which all celestial observations are reduced
C.the line from which a celestial body's altitude is measured
D.All of the above

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單項(xiàng)選擇題

Restricted areas at locks and dams are indicated by（）.

A.Flashing red lights upstream and fixed red lights downstream
B.Yellow unlighted buoys
C.Signs and/or flashing red lights
D.Red daymarks upstream and green daymarks downstream

單項(xiàng)選擇題

On a chart，the characteristic of the light on a lighthouse is shown as flashing white with a red sector.The red sector（）.

A.Indicates the limits of the navigable channel
B.Indicates a danger area
C.Is used to identify the characteristics of the light
D.Serves no significant purpose

The equator is（）.

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Restricted areas at locks and dams are indicated by（）.

On a chart，the characteristic of the light on a lighthouse is shown as flashing white with a red sector.The red sector（）.

On a chart，the characteristic of the light on a lighthouse is shown as flashing white with a red sector.The red sector（）.