The correct answer is C) Keep well clear of the vessel because she is on fire and has dangerous cargo on board or she is leaking dangerous cargo. The international signal flag "J" indicates that the vessel is on fire and has dangerous cargo on board, or that the vessel is leaking dangerous cargo. In this situation, the proper action is to keep well clear of the vessel, as the dangerous cargo or fire could pose a significant hazard. The other answer choices do not accurately reflect the meaning of the "J" signal flag.