单项选择题
A.the stand-on vessel may change course and speed at any time as it has the right of way
B.after the give-way vessel sounds one blast in a crossing situation
C.when action by the give-way vessel alone cannot prevent collision
D.when the two vessels become less than half a mile apart
单项选择题 Carbon dioxide flooding system is used for extinguishing fires because it reduces the concentration of oxygen in the air to（）.
单项选择题 Where shall the key to C02 room be kept?（）
单项选择题 Your vessel is crossing a narrow channel.A vessel to port is within the channel and crossing your course.She is showing a black cylinder.What is your responsibility?（）