单项选择题
（）is an area within the radiotelephone coverage of at least one VHF coast station in which continuous Digital Selective Calling is available.
A.Sea Area A1 B.Sea Area A2 C.Sea Area A3 D.Sea Area A4
单项选择题 What is the basic concept of GMDSS? （）
单项选择题 What is the action that a GMDSS Radio Operator should take when a DSC distress alert is received? （）
单项选择题 What is a GMDSS functional or carriage requirement for compulsory vessels?（）
