单项选择题
How does a coast radio station communicating by HF radio normally identify itself?（）
A.By its subscriber number B.By its call sign C.By its MMSI D.By its MID
单项选择题 How do you operate a portable CO2 fire extinguisher?（）
单项选择题 How do you determine the weight of the vessel that is supported by the ground when a vessel has run aground?（）
单项选择题 How do the height and location of a tug’s towing bitts relate to the danger of tripping?（）
