單項選擇題

The unit of duration of a dash in Morse Code is（）.

A.one and one-half times the length of a dot
B.twice the length of a dot
C.three times the length of a dot
D.four times the length of a dot

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單項選擇題

The range of a SSB transmission is MOST affected by（）.

A.atmospheric noise and radiated power
B.the frequency band selected and time of day or night
C.interference and position of the moon
D.radiated power and nearness to shore

單項選擇題

The light rhythm of Morse (A) is shown on（）.

A.preferred-channel buoys
B.starboard- or port-side buoys
C.special marks
D.safe water buoys