单项选择题

在GMDSS系统MF/HF波段的遇险,紧急与安全频率中,主要有()波段

A.2,4,6,8,10,12,14,16,18,20,20,25MHz
B.2,4,6,8,12,16,18,20,22,25MHz
C.2,4,6,8,10,12,14,16MHz
D.2,4,6,8,12,16MHz