问题
单项选择题
Radio beacon can be activated（）in case of distress.
A.only automatically
B.only manually
C.both automatically and manually
D.only by remote control
答案
参考答案：C
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Radio beacon can be activated（）in case of distress.
A.only automatically
B.only manually
C.both automatically and manually
D.only by remote control
参考答案：C