单项选择题
A.One to another B.One the other C.Each the other D.Each other
A.Situations when you can see vessels on radar that you cannot see visually B.Visibility of less than half a mile C.Any condition where visibility is restricted D.Visibility where you cannot see shore
A.a blast of from five to seven seconds' duration B.a blast of from five to six seconds' duration C.a blast of from four to six seconds' duration D.a blast of from six to seven seconds' duration