问题
单项选择题
Which of the following indicates a grave and imminent danger requesting immediate assistance on radio telephone?（）.
A.SOS
B.Mayday
C.Securite
D.PAN
答案
参考答案：B
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Which of the following indicates a grave and imminent danger requesting immediate assistance on radio telephone?（）.
A.SOS
B.Mayday
C.Securite
D.PAN
参考答案：B