单项选择题
The use of the danger signal（）.
A.replaces directional signals B.makes the other vessel the stand-on vessel C.indicates doubt as to another vessels actions D.is the same as a MAYDAY signal
单项选择题 The two main types of load cells used in mooring tension gauges are（）.
单项选择题 The transmission of messages respecting the dangers specified is free（）cost to the ships concerned.
单项选择题 The towing light is a(n)（）.
