A.if the compass bearing of an approaching vessel does not appreciably change
B.even when an appreciable bearing change is evident, particularly when approaching a vessel at close range
C.if you observe both sidelights of a vessel ahead for an extended period of time
D.All of the above

A.Both vessels must be power-driven
B.They must be meeting on reciprocal or nearly reciprocal courses
C.The situation must involve risk of collision
D.All of the above