99色精品-9色在线-99色在线-99色视频 国产欧美日产一区二区三区_亚洲精品亚洲人成在线观看_四虎在线精品永久观看_免费一级a一片久久精

單項選擇題

It is required that ships proceeding at sea should keep continuous watch on().

A.VHF channel16 and 13
B.appropriate DSC distress and safety frequency
C.INMARSAT TDM message channel
D.VHF channel 70 and channel 8

微信掃碼免費搜題