When two vessels are in immediate danger of collision，the stand-on vessel must（）.

单项选择题What would NOT be a distress signal?（）.

A.MAYDAY sent by radiotelephone
B.Continuous sounding of fog horn
C.Green star shells fired from a launcher
D.Square flag and ball in a vertical line

单项选择题An orange flag showing a black circle and square is a（）.

A.signal indicating a course change
B.distress signal
C.signal of asking to communicate with another vessel
D.signal indicating danger

单项选择题A distress signal（）.

A.consists of 5 or more short blasts of the fog signal apparatus
B.may be used separately or with other distress signals
C.consists of the raising and lowering of a large white flag
D.is used to indicate doubt about another vessel's intentions

单项选择题What is NOT a distress signal?（）

A.A continuous sounding of the fog horn
B.Firing a gun every minute
C.Five or more short rapid blasts on the whistle
D.A square flag and ball flown from the mast

单项选择题You receive a call from the MSA OF CHINA addressed to all stations. The call begins with the words Pan-Pan (3 times). Which type of emergency signal would this be?（）.

A.Safety signal
B.Urgency signal
C.Distress signal
D.Red alert signal