问题
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
答案
参考答案：D
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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
参考答案：D