单项选择题
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
单项选择题 On a chart，the characteristic of the light on a lighthouse is shown as flashing white with a red sector.The red sector（）.
单项选择题 In very high latitudes，the most practical chart projection is the（）.
单项选择题 How would you pass a red buoy in the maritime buoyage system“A” （）.
