BOTH INTERNATIONAL & INLAND Vessels of less than what length may not impede the passage of other vessels which can safely navigate only within a narrow channel or fairway?

Correct Answer: Option B — 20 meters

Rule 9(b) explicitly states that a vessel of less than 20 meters in length or a sailing vessel shall not impede the passage of a vessel which can safely navigate only within a narrow channel or fairway. This is a critical safety provision for large vessels restricted by draft.