单项选择题
A.Mate's license B.Restricted radiotelephone operator permit C.Second-class radio operator's license D.Seaman's document
The operation of which aids to navigation may be suspen...
单项选择题The operation of which aids to navigation may be suspended during war or national emergency（）.
A.Navigational satellites B.Loran C.Omega D.Any of the above
The loran lines drawn on navigation charts represent（）....
单项选择题The loran lines drawn on navigation charts represent（）.
A.Ground waves B.Skywaves C.Either ground waves or skywaves interchangeably D.An average between ground wave and skywave positions
The line connecting the Loran-C master station with a s...
单项选择题The line connecting the Loran-C master station with a secondary station is called the（）.
A.Focus line B.Base line C.Side line D.Center line
