BOTH INTERNATIONAL & INLAND 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 __________.

Correct Answer: Option C — avoid altering course toward a vessel abaft the beam

Rule 19(d) mandates that when a close-quarters situation is determined by radar alone, a vessel must avoid altering course toward a vessel abaft the beam. This prevents creating a new collision risk or worsening an existing one, as the other vessel's relative motion is already difficult to assess.