A.Whenever two vessels approach from opposite directions
B.If the bearing of an approaching vessel does not appreciably change
C.Whenever a vessel crosses ahead of the intended track of another vessel
D.If one vessel approaches another so as to be overtaking

A.not be regarded as a vessel
B.in general，keep well clear of all vessels
C.proceed at a slower speed than surrounding vessels
D.when making way，show the lights for a vessel not under command