单项选择题
A.is 50% water saturated
B.is 90% water saturated
C.temperature is greater than the dew point temperature
D.temperature is equal to，or below the dew point temperature
单项选择题 Five or more short blasts on a vessel’s whistle indicates that she is（）.
单项选择题 After a vessel transmits the original distress message，what signal should be sent to allow ships to take RDF bearings?（）
单项选择题 A message giving warning of a hurricane should have which prefix when sent by radiotelephone?（）