13. Avessel shall not cross a narrow channel of fairway if such crossing impedes the passage of a vessel which can safely navigate only within such channel of fairway. The later vessel may use the sound signal if in doubt as to the intention of the crossing vessel. “The later vessel” means:
(A) the crossing vessel
(B) the vessel which can safely navigate only within the narrow channel of fairway
(C) another vessel
(D) the vessel which will impede the passage