单项选择题
The quality of the message can be affected by（）.
A.climate B.sunshine C.human beings D.both a and b
单项选择题 The complying vessels can transmit ship-to-shore distress alerts by at least（）.
单项选择题 GMDSS is to provide（）with reliable communication .
单项选择题 IMO has decided that all ships over 300TGt must be fitted with a NAVTEX receiver（）.
