单项选择题
In using Loran-C，skywave reception gives greater range but is（）.
A.only accurate during daylight hours
B.much less accurate
C.only accurate at twilight
D.more accurate than using ground waves
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相关考题
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单项选择题
If the radio signal ground wave extends out for less distance than the minimum skywave distance，there is an area in which no signal is received．This is called the（）.
A.Skip zone
B.Blackout zone
C.Diffraction zone
D.Shadow zone -
单项选择题
Automatic identification systems（AIS）are required to（）.
A.provide safety-related information automatically to shore stations，other vessels and aircraft
B.receive safety-related information automatically from similarly equipped vessels
C.exchange safety-related information with shore-based facilities
D.All of the above -
单项选择题
（）is not a component of GPS.
A.He space component
B.Control component
C.User component
D.Alarming component
