单项选择题
Distress signals may be（）.
A.red flares B.smoke signals C.sound signals D.Any of the above
单项选择题 Distress flares and smoke signals for small passenger vessels（）.
单项选择题 At night，if you see a vessel ahead displaying the lights shown you should（）.
单项选择题 All of the following are recognized distress signals under the Navigation Rules EXCEPT（）.
