单项选择题
A.Watching the compass bearing of an approaching vessel B.Systematic observation of objects detected by radar C.Long-range radar scanning D.All of the above
A.Raising the antenna height increases the radar range B.The ability of radar to detect objects is unaffected by weather conditions C.Radar bearings are less accurate than radar ranges D.Radar should be checked regularly during clear weather to ensure that it is operating properly
A.Serrated range rings B.Indirect echoes C.Multiple echoes D.Blind sector