单项选择题
The International SafetyNet Service is able to address the call to（）.
A.all vessels B.selected groups of ships C.a particular ship D.A, B, C are all right
单项选择题 DSC distress relays can be transmitted by either（）or（）.
单项选择题 On-scene communications will normally take place between（）.
单项选择题 （）are used for distress alerting as a rule.
