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單項(xiàng)選擇題

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

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單項(xiàng)選擇題

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

單項(xiàng)選擇題

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