单项选择题
In restricted visibility, a vessel which detects by radar alone the presence of another vessel shall determine if a close quarters situation is developing or risk of collision exists. If so, she shall（）.
A.sound the danger signal B.when taking action, make only course changes C.avoid altering course toward a vessel abaft the beam D.All of the above
单项选择题 In revised editions of admiralty charts the（）are corrected first.
单项选择题 In the doldrums you can expect（）.
单项选择题 In the doldrums you will not have（）.
