单项选择题
Reliable delivery of messages is ensured by（）techniques.
A.forward error correction B.aftward error correction C.DGPS D.error-free and low error reception
单项选择题 How long must the GMDSS radio log be retained on board（）.
单项选择题 Each satellite broadcasts（）traffic on a designated channel.
单项选择题 At sea，all required GMDSS equipment（other than survival craft equipment）must be proven operational by（）.
