单项选择题 Your vessel has been damaged and is taking on water，but you do not require immediate assistance. You would preface a message advising other vessels of your situation with（）.

单项选择题 The urgency signal concerning the illness of persons on board ship is（）.

单项选择题 If you wished to transmit a message by voice concerning the safety of navigation，you would preface it by the word（）.