The correct answer is C) When it becomes apparent to you that the give-way vessel is not taking appropriate action. This is because the International Regulations for Preventing Collisions at Sea (COLREGS) state that the stand-on vessel (the vessel that has the right-of-way) should only take action to avoid collision if it becomes apparent that the give-way vessel is not taking appropriate action. The stand-on vessel should not take action unless this becomes clear, as it is the responsibility of the give-way vessel to take the necessary action to avoid collision. The other options are incorrect because A) is too broad, as the stand-on vessel should not take action simply because their course will cross ahead of the other vessel. B) is incorrect as the stand-on vessel cannot take action at any time they feel it is appropriate, and D) is incorrect as the stand-on vessel should not wait until extremis (a situation of immediate danger) before taking action.