The correct answer is D) All of the above. This is because, under both the International Rules (COLREGS) and the Inland Navigation Rules, the risk of collision may exist in the following situations: 1) If you observe both sidelights of a vessel ahead for an extended period of time, indicating the vessel is on a steady course and the risk of collision is increasing. 2) Even when an appreciable bearing change is evident, particularly when approaching a vessel at close range, as the risk of collision can still exist due to factors like speed and distance. 3) If the compass bearing of an approaching vessel does NOT appreciably change, as this indicates the vessels are on a constant bearing and the risk of collision is high. All of these scenarios, whether under International or Inland Rules, can indicate a risk of collision that must be carefully evaluated and addressed by the vessel operators.