单项选择题
You are making a telephone call ship-to-shore using the VHF-FM service.You can tell that the working channel is busy if you hear（）.
A.Speech B.Signaling tones C.A busy signal D.All of the above
单项选择题 Do you require any further assistance ? My ship is safe now and no assistance is necessary.This VHF communication generally takes place during（）.
单项选择题 （）both anchors.
单项选择题 The control of distress traffic is the responsibility of（）.
